- Email: [email protected]
Comparison of Real-Time Fluorescent Indocyanine Green and 99mTc-Nanocolloid Radiotracer Navigation in Sentinel Lymph Node Biopsy of Penile Cancer
Original Study
Comparison of Real-Time Fluorescent Indocyanine Green and 99mTc-Nanocolloid Radiotracer Navigation in Sentinel Lymph Node Biopsy of Penile Cancer Marcin Markuszewski,1 Wojciech Polom,1 Wojciech Cytawa,2 Piotr Czapiewski,3 Piotr Lass,2 Marcin Matuszewski1 Abstract We present a comparison of the 2 detection methods—radionuclide with technetium and fluorescent with indocyanine green—to identify sentinel lymph nodes for penile cancer. We obtained similar results in the identification of these nodes using 2 different detection techniques in 14 patients. Further studies are needed to assess the usefulness of a new technique. Introduction: The aim of this study was to compare lymphatic drainage patterns detected with fluorescent dye indocyanine green (ICG) with the lymphatic drainage patterns detected with radiotracer 99mTc-nanocolloid in dynamic sentinel node biopsy (DSNB) procedures. Patients and Methods: Fourteen patients with penile cancer and no palpable lymph nodes were included prospectively for DSNB. First, on the day of surgery 99mTc-nanocolloid was injected at the lesion site. Then, single photon emission computed tomography (SPECT) lymphoscintigraphy was performed. ICG was injected in the same manner as the radiotracer just before the surgery. In all cases partial penectomy and DSNB were performed. Sentinel lymph nodes (SLNs) were localized intraoperatively using the gammaray detection probe for radiocolloid and near infrared fluorescence (NIRF) camera for ICG. Results: Transcutaneously, lymphatic nodes were identified in all 14 patients using the gamma probe and in 10 patients using the NIRF camera. After skin incision, fluorescent nodes were observed using the NIRF camera in the remaining 4 patients. The examination led to identification of 32 SLNs in total using technetium and ICG and additionally 3 more nodes visible only using ICG. All SLNs found using SPECT were also fluorescent. In 3 patients ICG enabled only approximate localization of the SLNs. Of 35 SLNs, 30 were negative and 4 were positive for metastasis. Conclusion: Our analysis of the effectiveness of ICG compared with radiocolloid in the DSNB for penile cancer indicates that they are comparable with some specific advantages and disadvantages. These findings must be studied further in a larger group of patients. Clinical Genitourinary Cancer, Vol. -, No. -, --- ª 2015 Elsevier Inc. All rights reserved. Keywords: Near infrared fluorescence, Penile cancer, Radioguided lymphoscyntygraphy, Real-time navigation, Sentinel node biopsy
Introduction Penile squamous cell carcinoma (SCC) is a rare neoplasm in Western countries with incidence of approximately 1 per 100,000 1
Urology Department Nuclear Medicine Department 3 Pathomorphology Department Medical University of Gdansk, Gdansk, Poland 2
Submitted: Apr 2, 2015; Revised: Jun 20, 2015; Accepted: Jun 24, 2015 Address for correspondence: Wojciech Polom, MD, Urology Department, Medical University of Gdansk, Smoluchowskiego str 17, 80-214 Gdansk, Poland Fax: þ48583493170; e-mail contact: [email protected]
1558-7673/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2015.06.005
men per year. However, in some parts of the world it creates serious medical problems with the incidence reaching 10% to 20% of all malignant diseases in men.1 Pathologically, it is similar to SCC of the anus and oropharynx and vulvar, cervical, and vaginal SCC of the female genital tract. Surgery is the primary treatment option in localized penile cancer in cases with or without regional lymph node (LN) metastases. However, preoperative diagnosis of LNs in clinically N0 patients is still a diagnostic challenge,1 and especially if we know that the presence of nodal metastasis is a very important negative prognostic factor. To find metastases to LNs a complete inguinal LN dissection can be performed, which is also a potentially curative method and
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Fluorescent Versus Radiotracer Navigation in Penile Cancer
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a good staging procedure. However, it creates high morbidity and postoperative complications such as lymphocoele, lymphatic leakage, swelling of the scrotum and lower extremity, wound infection, and necrosis of the skin around the resection.2 What is more, according to the literature, as few as approximately 20% of patients with penile cancer and nonpalpable inguinal LNs have nodal metastases. It appears that the standard inguinal LN dissection might be unnecessarily performed in 80% of patients.3 However, it should also be noted that the wait-and-see policy poses a greater danger of inguinal metastases being found at later stages of the disease and creates negative influence on the final oncological result. At present, the clinicians have at their disposal several prognostic integrated systems developed to better predict the presence of LN metastases, such as for example, the Penile Prognostic Index. This nomogram uses clinical and pathological data but its sensitivity and specificity is rather low.4 Inguinal ultrasound, computed tomography (CT), or magnetic resonance imaging are also not recommended by the European Association of Urology (EAU) as effective imaging technologies in detecting metastases in patients with cN0 disease. From the clinical studies we know that there are some promising new minimally invasive and noninvasive tests that might be helpful in the assessment of LNs in the case of this cancer. These include ultrasonography-guided fine-needle aspiration cytology, single photon emission (SPECT) CT and lymphotropic nanoparticleenhanced magnetic resonance imaging. However, they need further evaluation. Therefore, currently no preoperative test can definitely exclude the necessity of LN dissection in penile cancer.5,6 Squamous cell carcinoma metastasizes to regional LNs in a continuous manner without “skip lesions,” which was proven by Cabanas in 1977. He was estimating the anatomical position of the LN by performing lymphangiography.7 His early technique, however, was characterized by a high false negative rate and thus low sensitivity. Modified and improved techniques were presented by Catalona,8 and became an alternative method of staging, but were also characterized by early and late complications after surgery.9 Finally, the minimally invasive staging method, presented by Horenblas et al10 was able to achieve individualization of the dynamic sentinel node biopsy (DSNB) concept in penile cancer with a high sensitivity rate and low complication rate. Morton et al also introduced this method into the treatment of melanoma.11 Currently technique recommended by the EAU and used in the European reference centers is dynamic lymphoscintigraphy with isosulfan blue and 99mTc-sulfur nanocolloid used to identify sentinel LNs (SLNs) in patients with clinically nonpalpable inguinal LNs.12 The EAU recommends the DSNB method in all patients with no palpable inguinal nodes and disease stage T1G2.13 It might also be supplemented by SPECT-CT, which is not recommended for routine use, but might improve the detection rate. The results of the method are satisfactory, but its main disadvantage is the use of radioactivity, which requires extensive safety measures.6 There has appeared, in some recent literature, reports about another useful modifications that would help identify SLNs with the use of different tracers—fluorophores in near infrared light. One of them is standardly used methylene blue (MB), which is a heterocyclic aromatic compound with a diameter of 1.43 nm, 320 Da,
Clinical Genitourinary Cancer Month 2015
with an excitation peak of 670 nm, and an emission peak of 690 nm. A second one—indocyanine green (ICG)—is a tricarbocyanine amphiphilic probe, a molecule with a diameter of 1.2 nm, 776 Da, with an excitation peak of 807 nm, and an emission peak of 822 nm. These fluorophores are the only ones approved for use by the European Medicines Agency and the US Food and Drug Administration. New fluorophores also seem to be promising in other subspecialties of urology.14,15 Another modification that would help identify SLNs is the use of hybrid fluorescent-radioactive tracer ICG-99mTc-nanocolloid. Brouwer et al reported the same drainage patterns of 99mTc-nanocolloid and the fluorescent-radioactive hybrid.16 Frontado et al further stated that the addition of optical fluorescence imaging improved visualization and detection of the SLNs, compared with the blue dye used in the case of penile cancer and also other cancers.17 The aim of our study was to compare the drainage patterns of fluorescent dye ICG with the drainage patterns of a radiotracer 99m Tc-nanocolloid, which is a standard tracer in DSNB procedures in penile cancer. Arguably, it might support the complete substitution of radioactive tracer with fluorescent dye.
Patients and Methods From May 2011 to June 2015, 14 patients diagnosed with penile cancer and no palpable LNs were included prospectively for the DSNB procedure. This study was approved by the local ethics committee and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All patients included in this study provided informed consent before inclusion in the study. Patients with palpable LNs were not included in the study group (Table 1). First, on the day of surgery in the Nuclear Medicine Department 99mTc-nanocolloid was administered in 4 intradermal injections at the lesion site proximal to the tumor into the healthy tissue (Figure 1). The activity of 1 mCi in 1 mL was used. Then, approximately 1 hour after radiotracer injection, SPECT-CT lymphoscintigraphy was performed using the Siemens Symbia T6 SPECT-CT dual-head gamma camera equipped with a 6row, spiral CT scanner. Acquisition parameters of SPECT-CT were: 128 128 matrix, 64 frames at 30 seconds each, low-dose CT without intravenous contrast media. The imaging time was approximately 30 minutes (Figure 2). Next, reconstruction and fusion of images was performed using the Syngo software 2008 (Siemens AG, Berlin and Munchen, Germany). Any focal activity of radiotracer detected in the local region, apart from the site of injection, was considered to correspond to SLN(s) and their localization was precisely described (Figure 3). Two to 4 hours after radiotracer injection, just before surgery, ICG (ICG-PULSION Medical Systems AG, Munchen, Germany) was injected at the lesion site in the same manner as the radiotracer. The reconstructed SPECT-CT images and information about localization of SLNs were available before surgery, which helped to better prepare for the procedure and very precisely locate the SLNs before surgery. In all cases partial penectomy and DSNB were performed. SLNs were localized intraoperatively using a hand-held gamma-ray detection probe (Neoprobe 2000, Neoprobe Corporation) for radiotracer detection (Figure 4) and near infrared fluorescence (NIRF) camera (Fluobeam; Fluoptics) for detection of ICG (Figure 5). The active LNs were resected and sent to the pathology department for detection of potential metastasis (Figure 6).
Marcin Markuszewski et al Figure 1 Radiotracer Injection
Table 1 Patient Characteristics Characteristic Patient n Mean Age (Range), Years Recurrence Number
Value 14 59.3 (42-87) 2 (1 local penile and 1 regional lymphatic with negative SLN after 9 months)
Tumor Stage, Number of Patients T1
11
T2
3
Tumor Grade G1
6
G2
5
G3
3
Groins, n
25
pN0
21
pN1
4
LNs Visualized Using ICG LNs Visualized Using Radiocolloid Mean BMI (Range) Follow-Up Range, Months
35 32 26.05 (23.4-29.2) 1-50
Tumor Position Glans penis
8
Glans penis and foreskin
6
Abbreviations: BMI ¼ body mass index; ICG ¼ indocyanine green; LN ¼ lymph node; p ¼ pathologic; SLN ¼ sentinel lymph node.
Sentinel LN Analysis
Specimens marked as “SLNs” were delivered to the laboratory of pathology in a separate container with buffered formalin. After overnight fixation the tissue was then searched for the presence of LNs. Every identified LN was described in the following categories: maximal size, color, structure, presence of dye, and any macroscopically visible changes, especially creamy foci suggestive of metastases. Later, every identified LN was separately prepared for histopathological analysis. The long axis of LNs were identified and LNs were cut transversely into 2-mm thick slices. They were later put in tissue cassettes, with a maximum of 3 slices per cassette and afterward the cassettes were transmitted for tissue processing. At the final stage of preparation, tissue was embedded in paraffin, cut into 4-mm slices, and stained with hematoxylin and eosin (H & E). At least 2 sections of every block was prepared. H & E-stained slides were evaluated by an experienced, certified histopathologist for the presence and size of metastatic foci. Patients for whom the final score showed no histological metastases in SLN were followed. Patient diagnosed with metastasis to the SLN underwent radical inguinal lymphadenectomy.
with a NIRF camera also in all 14 patients. The total number of identified SLNs was 35. From those nodes 32 were identified using technetium and ICG with an additional 3 more nodes visible only using ICG. Most importantly, all SLNs found using SPECT-CT and gamma-ray detection probe were also fluorescent but none of the 3 SLNs identified with ICG alone were seen during SPECT-CT scanning. Figure 2 Patient During Single Photon Emission Computed Tomography
Results Transcutaneously the SLNs were identified in all 14 patients using 99mTc-nanocolloid. All of these LNs were seen preoperatively in SPECT-CT scans. Transcutaneously the SLNs were observed using a NIRF camera and ICG in 10 patients. After subsequent skin incision and tissue preparation, fluorescent SLNs were observed
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Fluorescent Versus Radiotracer Navigation in Penile Cancer Figure 3 3D Reconstructed Single Photon Emission Computed Tomography Image of Sentinel Lymph Nodes
Intraoperatively (2-4 hours after 99mTc-nanocolloid and immediately after ICG injection) all preoperatively identified SLNs in the SPECT-CT scan could be localized using radio and fluorescence guidance. However, in 4 patients ICG enabled only approximate localization of the SLNs because of the visible fluorescent lymph outflow, indicating SLN localization. Three of those patients were obese with a body mass index (BMI) of 28, 28.8, and 29.2, and 1 of them had a BMI of 23. The localization was possible only after skin incision and some preparation. The findings in vivo were similar to ex vivo findings with the added finding of 3 additional fluorescent nodes that were not seen on SPECT-CT scans or when gamma-ray detection probes were used. We did not observe any adverse reactions. From 35 SLNs, 31 were negative and 4 were positive for metastasis in final histopathological examination. In addition, those nodes were radioactively and fluorescently labeled. In 3 cases we identified SLNs unilaterally and in 11 cases SLNs were identified in
Figure 4 Preoperative Sentinel Lymph Node Identification Using a Hand-Held Gamma-Ray Detection Probe
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Figure 5 Near Infrared Fluorescence Camera (Fluobeam; Fluoptics)
the groin area on both sides. In patients in whom SLNs were found on 1 side, 1 patient had 1 SLN identified and 2 patients had 2 SLNs identified. In the case of patients with SLNs identified on both sides, 7 patients had 1 SLN identified on each side and 4 patients had 2 SLNs identified on both sides. Additional fluorescent-only LNs were seen in 1 patient in both inguinal sites and in 1 patient in only 1 inguinal site. Additional fluorescent-only LNs were not metastatic and all SLNs in these patients were negative for metastases. It is likely to assume that additionally fluorescent LNs were second-tier SLNs because the ICG molecule is smaller than radiocolloid particles commonly used. It is possible for ICG particles because of their size to get from the first to the next LN but it is not clear why did it happened in those 3 patients only rather than in the whole group of patients. In all cases only fluorescent nodes were located in a group of inguinal nodes close to the radiofluorescent nodes. In 3 obese patients ICG enabled only approximate localization of the SLNs because of the visible fluorescent lymph outflow. Finding the exact location of these nodes was possible after skin incision over the place indicated by the outflow of lymph and subcutaneous tissue preparation. The thickness of the adipose tissue in those cases Figure 6 Fluorescent Sentinel Lymph Node Seen in Infrared Light After Excision
Marcin Markuszewski et al Table 2 Sentinel Lymph Nodes Analysis Patient Number
Tumor Localization
1
7
Glans penis near urethra Glans penis and foreskin Glans penis and foreskin Glans penis near urethra Glans penis Glans penis and foreskin Glans penis
8 9
2 3 4 5 6
10 11 12
Histopathology (Carcinoma Planoepitheliale)
SLNs, SLNs Lymphoscintigraphy TchSLN(s) ICG Detected Detected Detected
SLN Localization
T
N
M
G3
1
1
2
Inguinal nodes right
1b
1
x
G3
4
4
4
1b
0
x
G1
1
1
1
Inguinal nodes right and left Inguinal nodes left
1a
0
x
G1
2
2
4
1a
0
x
G1 G1
2 2
2 2
2 2
1b 1a
0 0
x x
G3
2
2
2
1b
0
x
Glans penis
G1
4
4
4
1a
0
x
Glans penis and foreskin Glans penis and foreskin Glans penis
G1
2
2
2
1a
0
x
G2
4
4
4
2
0
x
G2
2
2
2
Inguinal nodes right and left Inguinal nodes right Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left, external iliac left Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left Inguinal node right and left Inguinal nodes right and left
2
0
x
2
0
x
1b
2
x
1a
1
x
G2
2
2
2
13
Glans penis and foreskin Glans penis
G2
2
2
2
14
Glans penis
G2
2
2
2
Abbreviations: SLN ¼ sentinel lymph node; Tch ¼ technetium radiocolloid.
calculated from the skin surface to a node was approximately 2.4-3.3 cm. Ex vivo, similar to in vivo, all 32 SLNs were radioactive and fluorescent and 3 additional LNs were fluorescent only. We did not observe any adverse reactions after administration of the radiotracer or ICG. From 35 SLNs, 31 nodes were negative and 4 were positive for metastasis in final histopathological examination; these LNs were both radio- and fluorescent active (Table 2).
Follow-Up Our patients were seen in the outpatient clinic at 3-month intervals during the first 2 years after surgery, then in the third year, every 6 months to date. The last 2 patients who received surgery in June 2015 still wait for their first control. We observe patients for a total of 50 months (range, 1-50 months). One patient was lost to follow-up after their first control. All patients were instructed how to perform regular self-examination and report any observations. Control consisted of physical examination of penis and inguinal regions, then ultrasound examination of the groin and CT imaging were performed. We observed 1 local recurrence and 1 regional recurrence. In the case of local recurrence total penectomy was performed, in the case of regional recurrence, total bilateral inguinal and pelvic lymphadenectomy was performed. Prolonged lymph leakage was observed in 2 patients (14.2%) and lymphedema of the scrotum and legs in 5 patients (35.7%). Four patients (28.5%) were treated because of wound infection. We noticed the decrease in
complications after several procedures. We also noticed a persistent green color at the site of injection of ICG on the penis in 3 patients, which subsided after a couple of months.
Discussion Despite the increased use of ICG in the DSNB for breast,18 colon,19 melanoma,20 and other cancers,21 there have only been 4 studies to our knowledge on the use of ICG in the DSNB for penile cancer. Estimation of the stage of penile cancer using DSNB with the use of technetium radiocolloid and MB are commonly used diagnostic methods. According to Kroon et al, in a group of 140 patients with inguinal LNs not suspected to be cancerous, false negative results were obtained in 6 patients (16%).9 Currently there are a few other successful reports of ICG used for the diagnosis of SLNs in penile cancer.16,17,22 In a publication of Brouwer he used a fluorescent tracer hybrid of ICG combined with 99mTc-nanocolloid. In the group of 65 patients in whom ICG with 99mTc-nanocolloid was used compared with those in whom the MB was used, there was a much higher number of detected SLNs (96.8% vs. 55.7%; P < .0001). From his study it might be concluded that the use of vision and white light only with MB as a dye is less sensitive than using ICG dye visualized in near infrared light. According to Brouwer, one of the possibilities for the greater sensitivity of ICG compared with MB is easy and fast outflow of MB to the next nodal stations.16
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One of the problems in the detection of SLNs with NIRF is its limited penetration through adipose tissue. According to Pleijhuis et al, in the experimental study on breast, phantom ICG was possible to be detected at a depth of approximately 21 mm,23 and in the clinical situation in approximately 5-10 mm as mentioned by Ogasawara et al.24 Therefore, this is raised as a disadvantage in the diagnosis of SLNs in obese patients with a thick layer of fatty tissue. In our study, percutaneous detection was possible in 8, and after tissue preparation, in all 12 patients. However in the Brouwer report16 only 3.2% of SLNs could not be visualized in near infrared light intraoperatively, probably because of a thick layer of fatty tissue above the node. In our study, percutaneous detection was possible in 8, but after skin incision and tissue preparation, in all 12 patients. Another interesting finding, also discussed in publications regarding the lymph outflow in breast cancer and melanoma of the skin, is a greater number of LNs stained with ICG compared with technetium radiocolloid. In our study, 28 SLNs were radio- and fluorescent active and 3 more nodes were only fluorescent active, which was also confirmed in other publications, in patients with skin melanoma for whom additionally 4 LNs were excised and in 3 patients who were stained only with ICG or ICG combined with human serum albumin. In 2 patients, primary melanoma was on the lower leg and in 1 patient it was on his back.20 In the report from Sevick-Muraca et al on breast cancer it was shown, that using the radiocolloid, an average of 1.9 nodes were detected in the patient group; whereas the group in whom the ICG dose was > 10 mg had an average detection rate of 2.42 nodes.25 Tagaya et al showed an average of 2.3 SLNs detected using MB dye, and use of near infrared-guided ICG navigation yielded a higher detection rate of 5.5 SLNs (range, 1-10).26 We speculate that this might be because of the low molecular weight and higher degree of diffusion of ICG, which results in staining of second-station axillary LNs. The authors described in the group of 49 patients additionally, ICG detected 10 additional SLNs in 8 patients, and 3 additional SLNs were detected using ICG:human serum albumin in 3 patients.18 In publications in which the usage of a hybrid compound of radiocolloid and ICG is described, the authors do not describe a higher number of LNs stained using ICG and this is despite the fact that the hybrid compound is administered 3-27 hours before surgery, which must prove the high stability of the hybrid compound. Based on these combined results, the hybrid tracer ICG-99mTc nanocolloid has already been successfully applied for SLN procedures in > 100 patients for various primary tumors such as prostate, breast, oral cavity malignancies, and melanomas (head and neck, trunk, extremities). Despite this fact, in one of the studied cases the authors found nodes that exclusively contained fluorescence.27 In the publication of Fujiwara et al in which for 7 patients with skin melanoma located on the lower extremities, lymph outflow was directed to the groin. In these 7 patients, 8 LNs were resected; of which 2 cases resulted as metastases. One of the advantages listed by the authors is the ability to plan the resection for SLNs thanks to easy mapping of subcutaneous lymphatic drainage being visible on the skin with fluorescence.28 However, in the study by Namikawa and Yamazaki, the SLNs were visualized in only 61.2% of 49 studied patients with melanoma before cutting the skin.29 The SLNs were visualized in all of these patients only after the skin was cut and tissues were prepared.
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Conclusion Our initial analysis of the effectiveness of ICG compared with radiocolloid in the DSNB for penile cancer indicates its advantages and disadvantages, which must be studied further in a larger group of patients. Ours is the first study, to our knowledge, to compare ICG with radiocolloid in SLN detection in penile cancer. ICG appears to be a good alternative for finding the SLNs with improvement in intraoperative fluorescence guidance. Its main advantages are low cost, lack of radioactivity, and well known longterm observations that show no adverse reaction for ICG in humans. Nevertheless, we have to acknowledge some limitations in the DSNB technique and different tracers for identifying SLNs as “gold standard.” Those limitations occur in patients in whom we observe unilateral lymphatic outflow. It is likely that the unilateral lack of lymphatic outflow from the tumor can be caused by metastatic tumor cells in the LN that block lymph drainage. In our group of patients there were 3 such cases and those patients should be strictly followed but there are no strict guidelines on how to manage such patients.
Clinical Practice Points To our knowledge, this is the first study to use ICG and a
radioactive tracer separately for SLN biopsy in penile cancer patients. We described the early clinical results of sentinel node biopsy in this group of patients in whom we used the combination radioactive colloid method and the ICG fluorescence method. The lymphatic drainage patterns of the 2 methods were compared. There are not many reports about the usage of ICG in penile cancer patients. Brouwer et al16 described in 2014 the usage of combined ICG and technetium-nanocolloid. This method led to a high SLN detection rate in patients with penile carcinoma. More nodes were ICG-positive compared with gamma tracer and this potentially might result in a higher detection rate of ICG versus radioactive tracer. Fluorescent intraoperative identification of nodes in obese patients was less accurate compared with the radioactive method. The fluorescence method offers the advantage of successful intraoperative visual detection of the nodes. The fluorescence method also allows live visualization of lymphatic outflow to the nodes. The fluorescence method is potentially less expensive than other methods and might be achievable in the centers that do not have a nuclear medicine facility.
Acknowledgments We acknowledge the entire urological staff, and the nuclear medicine and pathology departments for their contribution.
Disclosure The authors have stated that they have no conflicts of interest.
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Marcin Markuszewski et al 3. Hughes BE, Leijte JA, Kroon BK, et al. Lymph node metastasis in intermediaterisk penile squamous cell cancer: a two-centre experience. Eur Urol 2010; 57: 688-92. 4. Kattan MW, Ficarra V, Artibani W, et al. Nomogram predictive of cancer-specific survival in patients undergoing partial or total amputation for squamous cell carcinoma of the penis. J Urol 2006; 175:2103-8. 5. Kayes O, Minhas S, Allen C, et al. The role of magnetic resonance imaging in the local staging of penile cancer. Eur Urol 2007; 51:1313-8, discussion 1318-9. 6. Brouwer OR, van den Berg NS, Mathéron HM, et al. Feasibility of intraoperative navigation to the sentinel node in the groin using preoperatively acquired single photon emission computerized tomography data: transferring functional imaging to the operating room. J Urol 2014; 192:1810-6. 7. Cabanas RM. An approach for the treatment of penile carcinoma. Cancer 1977; 39:456-66. 8. Catalona WJ. Modified inguinal lymphadenectomy for carcinoma of the penis with preservation of saphenous veins: technique and preliminary results. J Urol 1988; 140:306-10. 9. Kroon BK, Lont AP, Valdes Olmos RA, et al. Morbidity of dynamic sentinel node biopsy in penile carcinoma. J Urol 2005; 173:813-5. 10. Horenblas S, Jansen L, Meinhardt W, et al. Detection of occult metastasis in squamous cell carcinoma of the penis using a dynamic sentinel node procedure. J Urol 2000; 163:100-4. 11. Morton DL, Wen DR, Wong JH, et al. Technical details of intraoperative lymphatic mapping for early stage melanoma. Arch Surg 1992; 127:392-9. 12. Lont AP, Horenblas S, Tanis PJ, et al. Management of clinically node negative penile carcinoma: improved survival after the introduction of dynamic sentinel node biopsy. J Urol 2003; 170:783-6. 13. Pizzocaro G, Algaba F, Horenblas S, et al. EAU penile cancer guidelines 2009. Eur Urol 2010; 57:1002-12. 14. Polom W, Markuszewski M, Rho YS, et al. Usage of invisible near infrared light (NIR) fluorescence with indocyanine green (ICG) and methylene blue (MB) in urological oncology. Part 1. Cent European J Urol 2014; 67:142-8. 15. Polom W, Markuszewski M, Rho YS, et al. Use of invisible near infrared light fluorescence with indocyanine green and methylene blue in urology. Part 2. Cent European J Urol 2014; 67:310-3. 16. Brouwer OR, van den Berg NS, Mathéron HM, et al. A hybrid radioactive and fluorescent tracer for sentinel node biopsy in penile carcinoma as a potential replacement for blue dye. Eur Urol 2014; 65:600-9. 17. Frontado LM, Brouwer OR, van den Berg NS, et al. Added value of the hybrid tracer indocyanine green-99mTc-nanocolloid for sentinel node biopsy in a series of
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Comparison of Real-Time Fluorescent Indocyanine Green and 99mTc-Nanocolloid Radiotracer Navigation in Sentinel Lymph Node Biopsy of Penile Cancer Marcin Markuszewski,1 Wojciech Polom,1 Wojciech Cytawa,2 Piotr Czapiewski,3 Piotr Lass,2 Marcin Matuszewski1 Abstract We present a comparison of the 2 detection methods—radionuclide with technetium and fluorescent with indocyanine green—to identify sentinel lymph nodes for penile cancer. We obtained similar results in the identification of these nodes using 2 different detection techniques in 14 patients. Further studies are needed to assess the usefulness of a new technique. Introduction: The aim of this study was to compare lymphatic drainage patterns detected with fluorescent dye indocyanine green (ICG) with the lymphatic drainage patterns detected with radiotracer 99mTc-nanocolloid in dynamic sentinel node biopsy (DSNB) procedures. Patients and Methods: Fourteen patients with penile cancer and no palpable lymph nodes were included prospectively for DSNB. First, on the day of surgery 99mTc-nanocolloid was injected at the lesion site. Then, single photon emission computed tomography (SPECT) lymphoscintigraphy was performed. ICG was injected in the same manner as the radiotracer just before the surgery. In all cases partial penectomy and DSNB were performed. Sentinel lymph nodes (SLNs) were localized intraoperatively using the gammaray detection probe for radiocolloid and near infrared fluorescence (NIRF) camera for ICG. Results: Transcutaneously, lymphatic nodes were identified in all 14 patients using the gamma probe and in 10 patients using the NIRF camera. After skin incision, fluorescent nodes were observed using the NIRF camera in the remaining 4 patients. The examination led to identification of 32 SLNs in total using technetium and ICG and additionally 3 more nodes visible only using ICG. All SLNs found using SPECT were also fluorescent. In 3 patients ICG enabled only approximate localization of the SLNs. Of 35 SLNs, 30 were negative and 4 were positive for metastasis. Conclusion: Our analysis of the effectiveness of ICG compared with radiocolloid in the DSNB for penile cancer indicates that they are comparable with some specific advantages and disadvantages. These findings must be studied further in a larger group of patients. Clinical Genitourinary Cancer, Vol. -, No. -, --- ª 2015 Elsevier Inc. All rights reserved. Keywords: Near infrared fluorescence, Penile cancer, Radioguided lymphoscyntygraphy, Real-time navigation, Sentinel node biopsy
Introduction Penile squamous cell carcinoma (SCC) is a rare neoplasm in Western countries with incidence of approximately 1 per 100,000 1
Urology Department Nuclear Medicine Department 3 Pathomorphology Department Medical University of Gdansk, Gdansk, Poland 2
Submitted: Apr 2, 2015; Revised: Jun 20, 2015; Accepted: Jun 24, 2015 Address for correspondence: Wojciech Polom, MD, Urology Department, Medical University of Gdansk, Smoluchowskiego str 17, 80-214 Gdansk, Poland Fax: þ48583493170; e-mail contact: [email protected]
1558-7673/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2015.06.005
men per year. However, in some parts of the world it creates serious medical problems with the incidence reaching 10% to 20% of all malignant diseases in men.1 Pathologically, it is similar to SCC of the anus and oropharynx and vulvar, cervical, and vaginal SCC of the female genital tract. Surgery is the primary treatment option in localized penile cancer in cases with or without regional lymph node (LN) metastases. However, preoperative diagnosis of LNs in clinically N0 patients is still a diagnostic challenge,1 and especially if we know that the presence of nodal metastasis is a very important negative prognostic factor. To find metastases to LNs a complete inguinal LN dissection can be performed, which is also a potentially curative method and
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Fluorescent Versus Radiotracer Navigation in Penile Cancer
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a good staging procedure. However, it creates high morbidity and postoperative complications such as lymphocoele, lymphatic leakage, swelling of the scrotum and lower extremity, wound infection, and necrosis of the skin around the resection.2 What is more, according to the literature, as few as approximately 20% of patients with penile cancer and nonpalpable inguinal LNs have nodal metastases. It appears that the standard inguinal LN dissection might be unnecessarily performed in 80% of patients.3 However, it should also be noted that the wait-and-see policy poses a greater danger of inguinal metastases being found at later stages of the disease and creates negative influence on the final oncological result. At present, the clinicians have at their disposal several prognostic integrated systems developed to better predict the presence of LN metastases, such as for example, the Penile Prognostic Index. This nomogram uses clinical and pathological data but its sensitivity and specificity is rather low.4 Inguinal ultrasound, computed tomography (CT), or magnetic resonance imaging are also not recommended by the European Association of Urology (EAU) as effective imaging technologies in detecting metastases in patients with cN0 disease. From the clinical studies we know that there are some promising new minimally invasive and noninvasive tests that might be helpful in the assessment of LNs in the case of this cancer. These include ultrasonography-guided fine-needle aspiration cytology, single photon emission (SPECT) CT and lymphotropic nanoparticleenhanced magnetic resonance imaging. However, they need further evaluation. Therefore, currently no preoperative test can definitely exclude the necessity of LN dissection in penile cancer.5,6 Squamous cell carcinoma metastasizes to regional LNs in a continuous manner without “skip lesions,” which was proven by Cabanas in 1977. He was estimating the anatomical position of the LN by performing lymphangiography.7 His early technique, however, was characterized by a high false negative rate and thus low sensitivity. Modified and improved techniques were presented by Catalona,8 and became an alternative method of staging, but were also characterized by early and late complications after surgery.9 Finally, the minimally invasive staging method, presented by Horenblas et al10 was able to achieve individualization of the dynamic sentinel node biopsy (DSNB) concept in penile cancer with a high sensitivity rate and low complication rate. Morton et al also introduced this method into the treatment of melanoma.11 Currently technique recommended by the EAU and used in the European reference centers is dynamic lymphoscintigraphy with isosulfan blue and 99mTc-sulfur nanocolloid used to identify sentinel LNs (SLNs) in patients with clinically nonpalpable inguinal LNs.12 The EAU recommends the DSNB method in all patients with no palpable inguinal nodes and disease stage T1G2.13 It might also be supplemented by SPECT-CT, which is not recommended for routine use, but might improve the detection rate. The results of the method are satisfactory, but its main disadvantage is the use of radioactivity, which requires extensive safety measures.6 There has appeared, in some recent literature, reports about another useful modifications that would help identify SLNs with the use of different tracers—fluorophores in near infrared light. One of them is standardly used methylene blue (MB), which is a heterocyclic aromatic compound with a diameter of 1.43 nm, 320 Da,
Clinical Genitourinary Cancer Month 2015
with an excitation peak of 670 nm, and an emission peak of 690 nm. A second one—indocyanine green (ICG)—is a tricarbocyanine amphiphilic probe, a molecule with a diameter of 1.2 nm, 776 Da, with an excitation peak of 807 nm, and an emission peak of 822 nm. These fluorophores are the only ones approved for use by the European Medicines Agency and the US Food and Drug Administration. New fluorophores also seem to be promising in other subspecialties of urology.14,15 Another modification that would help identify SLNs is the use of hybrid fluorescent-radioactive tracer ICG-99mTc-nanocolloid. Brouwer et al reported the same drainage patterns of 99mTc-nanocolloid and the fluorescent-radioactive hybrid.16 Frontado et al further stated that the addition of optical fluorescence imaging improved visualization and detection of the SLNs, compared with the blue dye used in the case of penile cancer and also other cancers.17 The aim of our study was to compare the drainage patterns of fluorescent dye ICG with the drainage patterns of a radiotracer 99m Tc-nanocolloid, which is a standard tracer in DSNB procedures in penile cancer. Arguably, it might support the complete substitution of radioactive tracer with fluorescent dye.
Patients and Methods From May 2011 to June 2015, 14 patients diagnosed with penile cancer and no palpable LNs were included prospectively for the DSNB procedure. This study was approved by the local ethics committee and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All patients included in this study provided informed consent before inclusion in the study. Patients with palpable LNs were not included in the study group (Table 1). First, on the day of surgery in the Nuclear Medicine Department 99mTc-nanocolloid was administered in 4 intradermal injections at the lesion site proximal to the tumor into the healthy tissue (Figure 1). The activity of 1 mCi in 1 mL was used. Then, approximately 1 hour after radiotracer injection, SPECT-CT lymphoscintigraphy was performed using the Siemens Symbia T6 SPECT-CT dual-head gamma camera equipped with a 6row, spiral CT scanner. Acquisition parameters of SPECT-CT were: 128 128 matrix, 64 frames at 30 seconds each, low-dose CT without intravenous contrast media. The imaging time was approximately 30 minutes (Figure 2). Next, reconstruction and fusion of images was performed using the Syngo software 2008 (Siemens AG, Berlin and Munchen, Germany). Any focal activity of radiotracer detected in the local region, apart from the site of injection, was considered to correspond to SLN(s) and their localization was precisely described (Figure 3). Two to 4 hours after radiotracer injection, just before surgery, ICG (ICG-PULSION Medical Systems AG, Munchen, Germany) was injected at the lesion site in the same manner as the radiotracer. The reconstructed SPECT-CT images and information about localization of SLNs were available before surgery, which helped to better prepare for the procedure and very precisely locate the SLNs before surgery. In all cases partial penectomy and DSNB were performed. SLNs were localized intraoperatively using a hand-held gamma-ray detection probe (Neoprobe 2000, Neoprobe Corporation) for radiotracer detection (Figure 4) and near infrared fluorescence (NIRF) camera (Fluobeam; Fluoptics) for detection of ICG (Figure 5). The active LNs were resected and sent to the pathology department for detection of potential metastasis (Figure 6).
Marcin Markuszewski et al Figure 1 Radiotracer Injection
Table 1 Patient Characteristics Characteristic Patient n Mean Age (Range), Years Recurrence Number
Value 14 59.3 (42-87) 2 (1 local penile and 1 regional lymphatic with negative SLN after 9 months)
Tumor Stage, Number of Patients T1
11
T2
3
Tumor Grade G1
6
G2
5
G3
3
Groins, n
25
pN0
21
pN1
4
LNs Visualized Using ICG LNs Visualized Using Radiocolloid Mean BMI (Range) Follow-Up Range, Months
35 32 26.05 (23.4-29.2) 1-50
Tumor Position Glans penis
8
Glans penis and foreskin
6
Abbreviations: BMI ¼ body mass index; ICG ¼ indocyanine green; LN ¼ lymph node; p ¼ pathologic; SLN ¼ sentinel lymph node.
Sentinel LN Analysis
Specimens marked as “SLNs” were delivered to the laboratory of pathology in a separate container with buffered formalin. After overnight fixation the tissue was then searched for the presence of LNs. Every identified LN was described in the following categories: maximal size, color, structure, presence of dye, and any macroscopically visible changes, especially creamy foci suggestive of metastases. Later, every identified LN was separately prepared for histopathological analysis. The long axis of LNs were identified and LNs were cut transversely into 2-mm thick slices. They were later put in tissue cassettes, with a maximum of 3 slices per cassette and afterward the cassettes were transmitted for tissue processing. At the final stage of preparation, tissue was embedded in paraffin, cut into 4-mm slices, and stained with hematoxylin and eosin (H & E). At least 2 sections of every block was prepared. H & E-stained slides were evaluated by an experienced, certified histopathologist for the presence and size of metastatic foci. Patients for whom the final score showed no histological metastases in SLN were followed. Patient diagnosed with metastasis to the SLN underwent radical inguinal lymphadenectomy.
with a NIRF camera also in all 14 patients. The total number of identified SLNs was 35. From those nodes 32 were identified using technetium and ICG with an additional 3 more nodes visible only using ICG. Most importantly, all SLNs found using SPECT-CT and gamma-ray detection probe were also fluorescent but none of the 3 SLNs identified with ICG alone were seen during SPECT-CT scanning. Figure 2 Patient During Single Photon Emission Computed Tomography
Results Transcutaneously the SLNs were identified in all 14 patients using 99mTc-nanocolloid. All of these LNs were seen preoperatively in SPECT-CT scans. Transcutaneously the SLNs were observed using a NIRF camera and ICG in 10 patients. After subsequent skin incision and tissue preparation, fluorescent SLNs were observed
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Fluorescent Versus Radiotracer Navigation in Penile Cancer Figure 3 3D Reconstructed Single Photon Emission Computed Tomography Image of Sentinel Lymph Nodes
Intraoperatively (2-4 hours after 99mTc-nanocolloid and immediately after ICG injection) all preoperatively identified SLNs in the SPECT-CT scan could be localized using radio and fluorescence guidance. However, in 4 patients ICG enabled only approximate localization of the SLNs because of the visible fluorescent lymph outflow, indicating SLN localization. Three of those patients were obese with a body mass index (BMI) of 28, 28.8, and 29.2, and 1 of them had a BMI of 23. The localization was possible only after skin incision and some preparation. The findings in vivo were similar to ex vivo findings with the added finding of 3 additional fluorescent nodes that were not seen on SPECT-CT scans or when gamma-ray detection probes were used. We did not observe any adverse reactions. From 35 SLNs, 31 were negative and 4 were positive for metastasis in final histopathological examination. In addition, those nodes were radioactively and fluorescently labeled. In 3 cases we identified SLNs unilaterally and in 11 cases SLNs were identified in
Figure 4 Preoperative Sentinel Lymph Node Identification Using a Hand-Held Gamma-Ray Detection Probe
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Figure 5 Near Infrared Fluorescence Camera (Fluobeam; Fluoptics)
the groin area on both sides. In patients in whom SLNs were found on 1 side, 1 patient had 1 SLN identified and 2 patients had 2 SLNs identified. In the case of patients with SLNs identified on both sides, 7 patients had 1 SLN identified on each side and 4 patients had 2 SLNs identified on both sides. Additional fluorescent-only LNs were seen in 1 patient in both inguinal sites and in 1 patient in only 1 inguinal site. Additional fluorescent-only LNs were not metastatic and all SLNs in these patients were negative for metastases. It is likely to assume that additionally fluorescent LNs were second-tier SLNs because the ICG molecule is smaller than radiocolloid particles commonly used. It is possible for ICG particles because of their size to get from the first to the next LN but it is not clear why did it happened in those 3 patients only rather than in the whole group of patients. In all cases only fluorescent nodes were located in a group of inguinal nodes close to the radiofluorescent nodes. In 3 obese patients ICG enabled only approximate localization of the SLNs because of the visible fluorescent lymph outflow. Finding the exact location of these nodes was possible after skin incision over the place indicated by the outflow of lymph and subcutaneous tissue preparation. The thickness of the adipose tissue in those cases Figure 6 Fluorescent Sentinel Lymph Node Seen in Infrared Light After Excision
Marcin Markuszewski et al Table 2 Sentinel Lymph Nodes Analysis Patient Number
Tumor Localization
1
7
Glans penis near urethra Glans penis and foreskin Glans penis and foreskin Glans penis near urethra Glans penis Glans penis and foreskin Glans penis
8 9
2 3 4 5 6
10 11 12
Histopathology (Carcinoma Planoepitheliale)
SLNs, SLNs Lymphoscintigraphy TchSLN(s) ICG Detected Detected Detected
SLN Localization
T
N
M
G3
1
1
2
Inguinal nodes right
1b
1
x
G3
4
4
4
1b
0
x
G1
1
1
1
Inguinal nodes right and left Inguinal nodes left
1a
0
x
G1
2
2
4
1a
0
x
G1 G1
2 2
2 2
2 2
1b 1a
0 0
x x
G3
2
2
2
1b
0
x
Glans penis
G1
4
4
4
1a
0
x
Glans penis and foreskin Glans penis and foreskin Glans penis
G1
2
2
2
1a
0
x
G2
4
4
4
2
0
x
G2
2
2
2
Inguinal nodes right and left Inguinal nodes right Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left, external iliac left Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left Inguinal nodes right and left Inguinal node right and left Inguinal nodes right and left
2
0
x
2
0
x
1b
2
x
1a
1
x
G2
2
2
2
13
Glans penis and foreskin Glans penis
G2
2
2
2
14
Glans penis
G2
2
2
2
Abbreviations: SLN ¼ sentinel lymph node; Tch ¼ technetium radiocolloid.
calculated from the skin surface to a node was approximately 2.4-3.3 cm. Ex vivo, similar to in vivo, all 32 SLNs were radioactive and fluorescent and 3 additional LNs were fluorescent only. We did not observe any adverse reactions after administration of the radiotracer or ICG. From 35 SLNs, 31 nodes were negative and 4 were positive for metastasis in final histopathological examination; these LNs were both radio- and fluorescent active (Table 2).
Follow-Up Our patients were seen in the outpatient clinic at 3-month intervals during the first 2 years after surgery, then in the third year, every 6 months to date. The last 2 patients who received surgery in June 2015 still wait for their first control. We observe patients for a total of 50 months (range, 1-50 months). One patient was lost to follow-up after their first control. All patients were instructed how to perform regular self-examination and report any observations. Control consisted of physical examination of penis and inguinal regions, then ultrasound examination of the groin and CT imaging were performed. We observed 1 local recurrence and 1 regional recurrence. In the case of local recurrence total penectomy was performed, in the case of regional recurrence, total bilateral inguinal and pelvic lymphadenectomy was performed. Prolonged lymph leakage was observed in 2 patients (14.2%) and lymphedema of the scrotum and legs in 5 patients (35.7%). Four patients (28.5%) were treated because of wound infection. We noticed the decrease in
complications after several procedures. We also noticed a persistent green color at the site of injection of ICG on the penis in 3 patients, which subsided after a couple of months.
Discussion Despite the increased use of ICG in the DSNB for breast,18 colon,19 melanoma,20 and other cancers,21 there have only been 4 studies to our knowledge on the use of ICG in the DSNB for penile cancer. Estimation of the stage of penile cancer using DSNB with the use of technetium radiocolloid and MB are commonly used diagnostic methods. According to Kroon et al, in a group of 140 patients with inguinal LNs not suspected to be cancerous, false negative results were obtained in 6 patients (16%).9 Currently there are a few other successful reports of ICG used for the diagnosis of SLNs in penile cancer.16,17,22 In a publication of Brouwer he used a fluorescent tracer hybrid of ICG combined with 99mTc-nanocolloid. In the group of 65 patients in whom ICG with 99mTc-nanocolloid was used compared with those in whom the MB was used, there was a much higher number of detected SLNs (96.8% vs. 55.7%; P < .0001). From his study it might be concluded that the use of vision and white light only with MB as a dye is less sensitive than using ICG dye visualized in near infrared light. According to Brouwer, one of the possibilities for the greater sensitivity of ICG compared with MB is easy and fast outflow of MB to the next nodal stations.16
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Fluorescent Versus Radiotracer Navigation in Penile Cancer
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One of the problems in the detection of SLNs with NIRF is its limited penetration through adipose tissue. According to Pleijhuis et al, in the experimental study on breast, phantom ICG was possible to be detected at a depth of approximately 21 mm,23 and in the clinical situation in approximately 5-10 mm as mentioned by Ogasawara et al.24 Therefore, this is raised as a disadvantage in the diagnosis of SLNs in obese patients with a thick layer of fatty tissue. In our study, percutaneous detection was possible in 8, and after tissue preparation, in all 12 patients. However in the Brouwer report16 only 3.2% of SLNs could not be visualized in near infrared light intraoperatively, probably because of a thick layer of fatty tissue above the node. In our study, percutaneous detection was possible in 8, but after skin incision and tissue preparation, in all 12 patients. Another interesting finding, also discussed in publications regarding the lymph outflow in breast cancer and melanoma of the skin, is a greater number of LNs stained with ICG compared with technetium radiocolloid. In our study, 28 SLNs were radio- and fluorescent active and 3 more nodes were only fluorescent active, which was also confirmed in other publications, in patients with skin melanoma for whom additionally 4 LNs were excised and in 3 patients who were stained only with ICG or ICG combined with human serum albumin. In 2 patients, primary melanoma was on the lower leg and in 1 patient it was on his back.20 In the report from Sevick-Muraca et al on breast cancer it was shown, that using the radiocolloid, an average of 1.9 nodes were detected in the patient group; whereas the group in whom the ICG dose was > 10 mg had an average detection rate of 2.42 nodes.25 Tagaya et al showed an average of 2.3 SLNs detected using MB dye, and use of near infrared-guided ICG navigation yielded a higher detection rate of 5.5 SLNs (range, 1-10).26 We speculate that this might be because of the low molecular weight and higher degree of diffusion of ICG, which results in staining of second-station axillary LNs. The authors described in the group of 49 patients additionally, ICG detected 10 additional SLNs in 8 patients, and 3 additional SLNs were detected using ICG:human serum albumin in 3 patients.18 In publications in which the usage of a hybrid compound of radiocolloid and ICG is described, the authors do not describe a higher number of LNs stained using ICG and this is despite the fact that the hybrid compound is administered 3-27 hours before surgery, which must prove the high stability of the hybrid compound. Based on these combined results, the hybrid tracer ICG-99mTc nanocolloid has already been successfully applied for SLN procedures in > 100 patients for various primary tumors such as prostate, breast, oral cavity malignancies, and melanomas (head and neck, trunk, extremities). Despite this fact, in one of the studied cases the authors found nodes that exclusively contained fluorescence.27 In the publication of Fujiwara et al in which for 7 patients with skin melanoma located on the lower extremities, lymph outflow was directed to the groin. In these 7 patients, 8 LNs were resected; of which 2 cases resulted as metastases. One of the advantages listed by the authors is the ability to plan the resection for SLNs thanks to easy mapping of subcutaneous lymphatic drainage being visible on the skin with fluorescence.28 However, in the study by Namikawa and Yamazaki, the SLNs were visualized in only 61.2% of 49 studied patients with melanoma before cutting the skin.29 The SLNs were visualized in all of these patients only after the skin was cut and tissues were prepared.
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Conclusion Our initial analysis of the effectiveness of ICG compared with radiocolloid in the DSNB for penile cancer indicates its advantages and disadvantages, which must be studied further in a larger group of patients. Ours is the first study, to our knowledge, to compare ICG with radiocolloid in SLN detection in penile cancer. ICG appears to be a good alternative for finding the SLNs with improvement in intraoperative fluorescence guidance. Its main advantages are low cost, lack of radioactivity, and well known longterm observations that show no adverse reaction for ICG in humans. Nevertheless, we have to acknowledge some limitations in the DSNB technique and different tracers for identifying SLNs as “gold standard.” Those limitations occur in patients in whom we observe unilateral lymphatic outflow. It is likely that the unilateral lack of lymphatic outflow from the tumor can be caused by metastatic tumor cells in the LN that block lymph drainage. In our group of patients there were 3 such cases and those patients should be strictly followed but there are no strict guidelines on how to manage such patients.
Clinical Practice Points To our knowledge, this is the first study to use ICG and a
radioactive tracer separately for SLN biopsy in penile cancer patients. We described the early clinical results of sentinel node biopsy in this group of patients in whom we used the combination radioactive colloid method and the ICG fluorescence method. The lymphatic drainage patterns of the 2 methods were compared. There are not many reports about the usage of ICG in penile cancer patients. Brouwer et al16 described in 2014 the usage of combined ICG and technetium-nanocolloid. This method led to a high SLN detection rate in patients with penile carcinoma. More nodes were ICG-positive compared with gamma tracer and this potentially might result in a higher detection rate of ICG versus radioactive tracer. Fluorescent intraoperative identification of nodes in obese patients was less accurate compared with the radioactive method. The fluorescence method offers the advantage of successful intraoperative visual detection of the nodes. The fluorescence method also allows live visualization of lymphatic outflow to the nodes. The fluorescence method is potentially less expensive than other methods and might be achievable in the centers that do not have a nuclear medicine facility.
Acknowledgments We acknowledge the entire urological staff, and the nuclear medicine and pathology departments for their contribution.
Disclosure The authors have stated that they have no conflicts of interest.
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