- Email: [email protected]
Use of 3D-Ultrasound for Cervical Cancer Brachytherapy: An Imaging Technique to Improve Treatment Planning
S92
Abstracts / Brachytherapy 15 (2016) S21eS204
doses were then imported into an in-house-coded inverse optimization treatment planning program to obtain optimal plans for 12 patient cases. To evaluate quantitative effect of each shield, the transmission factor (TF) is defined by: Transmission factor5TF5(Dose(r,180 )/Dose (r,0 )), For re-plan optimizations, the conventional tandem-ring (T&R) is replaced by DMBT tandem-ring (DMBT&R). All plans with DMBT&R were compared with the standard T&R plans. Prescription dose was 15.0 or 17.50Gy. All plans were normalized to receive the same high risk-clinical target volume (HR-CTV) D90. The DVH parameters were calculated for HR-CTV (D100, D10, V100), and OARs bladder, sigmoid, and rectum (D2cc), respectively. The standard clinical plans are compared against the optimized plans with the DMBT&R MT-18C applicator, and other shield types are compared against the MT-18C alloy plans, [(DMBT(shield)/ DMBT(MT-18C)) -1]%. Results: The 2D-isodose distribution results around the conventional and 8 DMBT shields are presented in Figs. 1(b-j). All isodose lines of DMBT shield were superior to conventional tandem for OARs sparing and at least are similar for HR-CTV coverage. All DMBT isodose distributions shrinked in Y-axis direction as the Ir-192 source is collimated by 27.5 , and located 2.05mm away from the DMBT center. TF increased by increasing distance from the DMBT center, and is saturated at the end (Fig.1k). This is due to the decrease of the back spill radiations by increasing distance from the source, and due to the increased scattering in the forward directions. The TFs are close for Ir, Pt, and Os shields, and were the lowest among all metals considered. The TFs (r55cm,180 ) were 36.58%, 34.76%, 31.92%, 28.88%, 27.88%, 26.20%, 26.15%, 25.45%, for Ta, MT-18C, W, Re, Au, Os, Pt, and Ir, respectively. On average, rectum D2cc was reduced by 1.32%, 1.25%, 1.22%, 0.94%, 0.84%, 0.38% for Ir, Pt, Os, Au, Re, and W, relative to the MT-18C shield, respectively. This was increased by 0.28% for the Ta. On average, bladder D2cc was reduced by 0.85%, 0.78%, 0.75%, 0.60%, 0.51%, 0.24% for Ir, Pt, Os, Au, Re, and W shields, respectively. These values were reduced by 1.01%, 0.91%, 0.86%, 0.70%, 0.59%, and 0.23%, for sigmoid D2cc, respectively. The values for Ta in bladder and sigmoid D2cc increased by 0.08%, and 0.25%, respectively. Conclusions: The above quantitative results showed that for OARs sparing, Ir is the most effective shielding material. It may be best to construct the DMBT tandem applicator with the Ir shield but the clinical advantage is relatively small.
Fig. 1. a). Transverse view of the DMBT tandem applicator: (c-j) - 2D isodoses of the DMBT tandem applicator with 8 different shielding materials compared with a conventional tandem applicator (b). k) Transmission Factors (TF) plotted as distance.
GSOR12 Presentation Time: 3:40 PM Use of 3D-Ultrasound for Cervical Cancer Brachytherapy: An Imaging Technique to Improve Treatment Planning Patricia St-Amant, B. Eng1,2, William Foster, MD1, Marie-Anne Forment, MD1, Sylviane Aubin, MSc1, Luc Beaulieu, PhD1,2. 1Radiation Oncology, CHU de Quebec, Quebec, QC, Canada; 2Physique, genie physique et optique, Universite Laval, Quebec, QC, Canada. Purpose: To determine whether the use of 3DUS can improve cervical cancer BT treatment planning when compared to CT planning. Materials and Methods: 6 patients diagnosed with cervical squamous cell carcinoma were included in this study. They had FIGO stage IIB to IIIB disease. At the time of brachytherapy, a CT scan (Somaton Sensation, Siemens) with 2 mm slice thickness and a 3D transabdominal ultrasound scan (3DUS) (Clarity AutoScan prototype, Elekta, Montreal) were acquired for each patient in the same position just after the tandem and ovoids insertion within the brachysuite. The HR-CTV (including the cervix and residual disease at the time of brachytherapy) was contoured by a radiation oncologist on CT images, 3DUS and a fusion of these 2 imaging modalities (CT-3DUS). The bladder and rectum were contoured on CT images. The treatment was planned using the OncentraBrachy Treatment Planning System (Elekta Brachy, Veenendaal, The Netherlands). The optimization was initially performed on CT images. The CT-planned treatment dwell times were then copied on the 3DUS and on the fusion (CT-3DUS) treatment plans to report the dose to the HR-CTV delineated on each modality. Plans were then optimized once again using the HRCTV delineated on 3DUS and CT-3DUS to try to gain optimal coverage to the HR-CTV while limiting the dose to the OARs. The HR-CTV coverage (V100) was evaluated on the various modalities, while the OARs D2cc were all evaluated on CT as they were not always visible on 3DUS; the latter was performed by transferring the 3DUS optimized plans back on CT. Results: 3DUS gave additional information to the physician in an effort to improve the delineation of HR-CTV, including the tumor extensions that were not visible on CT. On average, volumes delineated using the 3DUS or the CT-3DUS were smaller than the ones on CT by (1115)% and (1427)%, respectively. As a result, the HR-CTV V100 appeared improved for 4 patients out of 6 for plans optimized on CT and copied on CT-3DUS and similarly for 4 out of 6 for plans copied on 3DUS, as seen in Fig. 1a. In most cases, optimization on CT-3DUS and 3DUS allowed for a better compromise between HR-CTV coverage and dose of the OARs (Fig. 1b-1d). The coverage can be extended from (944)% for CT up to (964)% for the CT-3DUS and up to (973)% for 3DUS. The benefits of the 3DUS technique are different for each patient and allow personalized treatment for each of them. In our experience, 3DUS alone could not be used at this point for 3D treatment planning due to some limitations. First, 3DUS is a new imaging modality in the domain and we experienced more variations in target delineation when compared to CT and CT-3DUS. As a result, one patient had HR-CTV extensions on 3DUS, unseen on CT, which resulted in a lower coverage when copying the CT treatment plan. There is a significant learning curve associated with the use of 3DUS, both for acquisition and image interpretation. Second, ovoids’ reconstruction based only on 3DUS was imprecise causing uncertainties in the planning. Finally, to ensure good HR-CTV visibility on 3DUS, the bladder had to be filled with fluids. Treatment planning on 3DUS alone may induce an increase in the bladder dose due to these fluids. Conclusions: The 3DUS system provides additional information about the target volume that could improve treatment planning. However, 3DUS alone does not allow the physician to delineate all of the OAR and it remains challenging to accurately identify the position of the ovoids. It has been previously shown that ultrasound imaging can be used for 2D planning [1] and it is an alternative to 2D X-rays-based planning. However, at this point, we believe that 3DUS needs to be combined with CT for volumebased 3D planning. Further performance comparison to MRI planning is ongoing in our institution. Reference [1] K. Narayan et al, IJROBP 75 (2009) 1529-1535.
Abstracts / Brachytherapy 15 (2016) S21eS204
Figure 1. A) V100(%) treatment plan optimized on CT and copied on CT-3DUS and 3DUS. B) V100(%) optimized on each modality. C) D2cc to bladder for the plan optimized on each modality and D) D2cc to rectum for plans optimized on each modality.
GSOR13 Presentation Time: 3:45 PM A Review of Practice and Outcomes of External Beam Radiotherapy Treatment with Concurrent Chemotherapy Followed by MRI-Assisted Intracavitary Brachytherapy for Locally Advanced Cervix Cancer Vivien Tse, MBBS, MSc1, Anna-Maria Shiarli, MBChB, BSc1, Sarah Aldridge, BSc, MSc2, Caroline Nahab, BSc1, Emma-Louise Jones, MPhys MSc2, Nebojsa Bozic, BSc, MSc2, Anna Winship, BMedSci BM, BS1, Vinod Mullassery, MD1. 1 Clinical Oncology, Guys and St Thomas NHS Foundation Trust, London, United Kingdom; 2Medical Physics, Guys and St Thomas NHS Foundation Trust, London, United Kingdom. Purpose: To evaluate the clinical outcomes of the first 100 patients treated at Guy’s and St Thomas’ Hospital NHS Foundation trust (GSTT) with radical chemoradiotherapy (CRT) followed by MRI-assisted HDR Intracavitary brachytherapy (HDR-ICBT) for locally advanced cervix cancer. Materials and Methods: Retrospective data was collected for 100 consecutive patients treated curatively with histologically proven cervical carcinoma between 2010 and 2015. CRT consisted of external beam radiotherapy to the pelvis þ/- para-aortic nodes (PA) of 45-50.4Gy in 25-28 fractions þ/- 5.4Gy boost to involved nodes with concurrent weekly cisplatin chemotherapy (40mg/m2). This was followed by 3 fractions of HDR-ICBT using Rotterdam tandem/ovoid applicator or Interstitial CT/MR ring. Interstitial needles were introduced in June 2012. MRI-assisted adaptive treatment planning was carried out as per GEC-ESTRO recommendations. Retrospective data was collected using electronic medical records, histopathology, radiology and dosimetry reports. Treatment outcomes were calculated using the actuarial life table method from date of biopsy, except for late toxicities which were calculated from date of completion of ICBT. 1 patient was excluded from this analysis as size of tumour at diagnosis was not recorded in medical records. Results: Median age was 50 years (range 25-86). 70% had FIGO stage 2B disease and 50% of the patients had node positive disease. Median tumour size (T) was 43mm and 77% patients had tumour size 5cm or less. In this study median follow up was 26.7 months. Median overall treatment time was 47 days and mean EQD2 to HRCTV D90 was 88.2Gy. Median HRCTV volume was 26.6cm3. 7% showed primary treatment failure (5% to cervix alone and 2% to in-field nodal disease (pelvic or PA node) only. 11% subsequently relapsed (2% developed isolated PA nodal recurrence,
S93
6% developed distant disease only, 3% developed synchronous locoregional and distant recurrence). Continuous cervical control was 91%. Rate of local control for true pelvis was 91.4% in those achieving D90 O88Gy. Overall Survival (OS) for all patients was 56.7% [79.0% for node negative (N0) patients and 36.0% in node positive (N1)]. Cancer Specific Survival (CSS) for all patients was 63.0% (82.9% for N0 and 38.4% for N1). Progression Free Survival (PFS) for all patients was 74.1% (79.0% T- 5cm or less and 59.0% TO5cm, for 91.2% N0 and 54.7% for N1). Overall locoregional control rates (LRC) (cervix and pelvic nodes) were 87.0% for all patients. LRC was 90.2% (95.4% Te5cm or less and 88.2% TO5cm) for the patient cohort treated following the introduction of interstitial needles in June 2012 compared to 78.2% prior to this. Incidence of grade 3 GI/GU/vaginal toxicity was 8% of patients had with 0% at grade 4. The most prevalent toxicity was G1 vaginal toxicity affecting 46% of patients. Conclusions: Rates for CR, relapse and PFS in this study are consistent with existing single centre reports using similar protocols with EBRT and MRIassisted HDR-ICBT showing improved local control and a reduced toxicity profile compared to non-3D techniques. It also supports evidence that outcomes improve with increasing experience and with the introduction of interstitial needles. This study supports evidence that tumour size at diagnosis has a negative impact on LRC and PFS. Our rates of local control O90% in those achieving HRCTV D90 O88Gy10 are consistent with existing literature. Equally, nodal status has a negative impact on PFS, CSS and OS. This supports the importance of image-guided brachytherapy and the need for further investigation in the role of systemic chemotherapy in the upfront treatment of locally advanced, node positive cervical cancers to improve outcomes.
GSOR14 Presentation Time: 3:50 PM Outpatient Interstitial ImplantseIntegrating Cesium131 Permanent Interstitial Brachytherapy into Definitive Treatment for Gynecologic Malignancies Jonathan Feddock, MD, Prakash Aryal, PhD, Charles Wooten, MD, Marcus Randall, MD. Radiation Medicine, University of Kentucky, Lexington, KY, USA. Purpose: Curative intent brachytherapy for gynecologic cancers most often involves intracavitary approaches. In the less common clinical scenarios that require interstitial brachytherapy, template-guided after-loading techniques (e.g. Syed-Neblett interstitial implants) are generally used, yet patients might not be offered this option due to perceived risks or limitations in facilities, equipment, and expertise. Permanent Interstitial Brachytherapy (PIB) with Cs-131 in the outpatient setting is a relatively new procedure that expands brachytherapy options for women who might benefit from interstitial treatment. Our experience suggests that this option is exceptionally effective and safe in the curative management of selected gynecologic cancers for whom interstitial radiation techniques are indicated. Materials and Methods: Between August 2012 and November 2015, 22 patients received a total of 25 Cesium-131 PIB procedures at our institution as a component of definitive therapy for gynecologic malignancy following pelvic radiation therapy (PRT) with/without intracavitary brachytherapy (ICB). Paterson-Parker rules were used to calculate activity and seed distribution. Cumulative doses were calculated using Biological Effective Dose (BED) and Equivalent Dose at 2 Gy per fraction (EQD2) formalism. Results: Median follow up was 16 months (range 1.3-39.4). Primary diagnoses included Uterus (n512), Cervix (n52), and Vaginal (n510). Cell types included squamous cell (n57), endometrioid adenocarcinoma (n57), melanoma (n53), serous (n52), adenosquamous (n51), clear cell (n51), and small cell (n51). Histologic grades included grade 1 (n54), grade 2 (n58) and grade 3 (n510). Indications for interstitial brachytherapy were gross residual disease with thickness 0.5-1.5 cm (n512), positive surgical margin (n54), and inability to undergo a Syed-Neblett template implant due to medical co-morbidities (n56).
Abstracts / Brachytherapy 15 (2016) S21eS204
doses were then imported into an in-house-coded inverse optimization treatment planning program to obtain optimal plans for 12 patient cases. To evaluate quantitative effect of each shield, the transmission factor (TF) is defined by: Transmission factor5TF5(Dose(r,180 )/Dose (r,0 )), For re-plan optimizations, the conventional tandem-ring (T&R) is replaced by DMBT tandem-ring (DMBT&R). All plans with DMBT&R were compared with the standard T&R plans. Prescription dose was 15.0 or 17.50Gy. All plans were normalized to receive the same high risk-clinical target volume (HR-CTV) D90. The DVH parameters were calculated for HR-CTV (D100, D10, V100), and OARs bladder, sigmoid, and rectum (D2cc), respectively. The standard clinical plans are compared against the optimized plans with the DMBT&R MT-18C applicator, and other shield types are compared against the MT-18C alloy plans, [(DMBT(shield)/ DMBT(MT-18C)) -1]%. Results: The 2D-isodose distribution results around the conventional and 8 DMBT shields are presented in Figs. 1(b-j). All isodose lines of DMBT shield were superior to conventional tandem for OARs sparing and at least are similar for HR-CTV coverage. All DMBT isodose distributions shrinked in Y-axis direction as the Ir-192 source is collimated by 27.5 , and located 2.05mm away from the DMBT center. TF increased by increasing distance from the DMBT center, and is saturated at the end (Fig.1k). This is due to the decrease of the back spill radiations by increasing distance from the source, and due to the increased scattering in the forward directions. The TFs are close for Ir, Pt, and Os shields, and were the lowest among all metals considered. The TFs (r55cm,180 ) were 36.58%, 34.76%, 31.92%, 28.88%, 27.88%, 26.20%, 26.15%, 25.45%, for Ta, MT-18C, W, Re, Au, Os, Pt, and Ir, respectively. On average, rectum D2cc was reduced by 1.32%, 1.25%, 1.22%, 0.94%, 0.84%, 0.38% for Ir, Pt, Os, Au, Re, and W, relative to the MT-18C shield, respectively. This was increased by 0.28% for the Ta. On average, bladder D2cc was reduced by 0.85%, 0.78%, 0.75%, 0.60%, 0.51%, 0.24% for Ir, Pt, Os, Au, Re, and W shields, respectively. These values were reduced by 1.01%, 0.91%, 0.86%, 0.70%, 0.59%, and 0.23%, for sigmoid D2cc, respectively. The values for Ta in bladder and sigmoid D2cc increased by 0.08%, and 0.25%, respectively. Conclusions: The above quantitative results showed that for OARs sparing, Ir is the most effective shielding material. It may be best to construct the DMBT tandem applicator with the Ir shield but the clinical advantage is relatively small.
Fig. 1. a). Transverse view of the DMBT tandem applicator: (c-j) - 2D isodoses of the DMBT tandem applicator with 8 different shielding materials compared with a conventional tandem applicator (b). k) Transmission Factors (TF) plotted as distance.
GSOR12 Presentation Time: 3:40 PM Use of 3D-Ultrasound for Cervical Cancer Brachytherapy: An Imaging Technique to Improve Treatment Planning Patricia St-Amant, B. Eng1,2, William Foster, MD1, Marie-Anne Forment, MD1, Sylviane Aubin, MSc1, Luc Beaulieu, PhD1,2. 1Radiation Oncology, CHU de Quebec, Quebec, QC, Canada; 2Physique, genie physique et optique, Universite Laval, Quebec, QC, Canada. Purpose: To determine whether the use of 3DUS can improve cervical cancer BT treatment planning when compared to CT planning. Materials and Methods: 6 patients diagnosed with cervical squamous cell carcinoma were included in this study. They had FIGO stage IIB to IIIB disease. At the time of brachytherapy, a CT scan (Somaton Sensation, Siemens) with 2 mm slice thickness and a 3D transabdominal ultrasound scan (3DUS) (Clarity AutoScan prototype, Elekta, Montreal) were acquired for each patient in the same position just after the tandem and ovoids insertion within the brachysuite. The HR-CTV (including the cervix and residual disease at the time of brachytherapy) was contoured by a radiation oncologist on CT images, 3DUS and a fusion of these 2 imaging modalities (CT-3DUS). The bladder and rectum were contoured on CT images. The treatment was planned using the OncentraBrachy Treatment Planning System (Elekta Brachy, Veenendaal, The Netherlands). The optimization was initially performed on CT images. The CT-planned treatment dwell times were then copied on the 3DUS and on the fusion (CT-3DUS) treatment plans to report the dose to the HR-CTV delineated on each modality. Plans were then optimized once again using the HRCTV delineated on 3DUS and CT-3DUS to try to gain optimal coverage to the HR-CTV while limiting the dose to the OARs. The HR-CTV coverage (V100) was evaluated on the various modalities, while the OARs D2cc were all evaluated on CT as they were not always visible on 3DUS; the latter was performed by transferring the 3DUS optimized plans back on CT. Results: 3DUS gave additional information to the physician in an effort to improve the delineation of HR-CTV, including the tumor extensions that were not visible on CT. On average, volumes delineated using the 3DUS or the CT-3DUS were smaller than the ones on CT by (1115)% and (1427)%, respectively. As a result, the HR-CTV V100 appeared improved for 4 patients out of 6 for plans optimized on CT and copied on CT-3DUS and similarly for 4 out of 6 for plans copied on 3DUS, as seen in Fig. 1a. In most cases, optimization on CT-3DUS and 3DUS allowed for a better compromise between HR-CTV coverage and dose of the OARs (Fig. 1b-1d). The coverage can be extended from (944)% for CT up to (964)% for the CT-3DUS and up to (973)% for 3DUS. The benefits of the 3DUS technique are different for each patient and allow personalized treatment for each of them. In our experience, 3DUS alone could not be used at this point for 3D treatment planning due to some limitations. First, 3DUS is a new imaging modality in the domain and we experienced more variations in target delineation when compared to CT and CT-3DUS. As a result, one patient had HR-CTV extensions on 3DUS, unseen on CT, which resulted in a lower coverage when copying the CT treatment plan. There is a significant learning curve associated with the use of 3DUS, both for acquisition and image interpretation. Second, ovoids’ reconstruction based only on 3DUS was imprecise causing uncertainties in the planning. Finally, to ensure good HR-CTV visibility on 3DUS, the bladder had to be filled with fluids. Treatment planning on 3DUS alone may induce an increase in the bladder dose due to these fluids. Conclusions: The 3DUS system provides additional information about the target volume that could improve treatment planning. However, 3DUS alone does not allow the physician to delineate all of the OAR and it remains challenging to accurately identify the position of the ovoids. It has been previously shown that ultrasound imaging can be used for 2D planning [1] and it is an alternative to 2D X-rays-based planning. However, at this point, we believe that 3DUS needs to be combined with CT for volumebased 3D planning. Further performance comparison to MRI planning is ongoing in our institution. Reference [1] K. Narayan et al, IJROBP 75 (2009) 1529-1535.
Abstracts / Brachytherapy 15 (2016) S21eS204
Figure 1. A) V100(%) treatment plan optimized on CT and copied on CT-3DUS and 3DUS. B) V100(%) optimized on each modality. C) D2cc to bladder for the plan optimized on each modality and D) D2cc to rectum for plans optimized on each modality.
GSOR13 Presentation Time: 3:45 PM A Review of Practice and Outcomes of External Beam Radiotherapy Treatment with Concurrent Chemotherapy Followed by MRI-Assisted Intracavitary Brachytherapy for Locally Advanced Cervix Cancer Vivien Tse, MBBS, MSc1, Anna-Maria Shiarli, MBChB, BSc1, Sarah Aldridge, BSc, MSc2, Caroline Nahab, BSc1, Emma-Louise Jones, MPhys MSc2, Nebojsa Bozic, BSc, MSc2, Anna Winship, BMedSci BM, BS1, Vinod Mullassery, MD1. 1 Clinical Oncology, Guys and St Thomas NHS Foundation Trust, London, United Kingdom; 2Medical Physics, Guys and St Thomas NHS Foundation Trust, London, United Kingdom. Purpose: To evaluate the clinical outcomes of the first 100 patients treated at Guy’s and St Thomas’ Hospital NHS Foundation trust (GSTT) with radical chemoradiotherapy (CRT) followed by MRI-assisted HDR Intracavitary brachytherapy (HDR-ICBT) for locally advanced cervix cancer. Materials and Methods: Retrospective data was collected for 100 consecutive patients treated curatively with histologically proven cervical carcinoma between 2010 and 2015. CRT consisted of external beam radiotherapy to the pelvis þ/- para-aortic nodes (PA) of 45-50.4Gy in 25-28 fractions þ/- 5.4Gy boost to involved nodes with concurrent weekly cisplatin chemotherapy (40mg/m2). This was followed by 3 fractions of HDR-ICBT using Rotterdam tandem/ovoid applicator or Interstitial CT/MR ring. Interstitial needles were introduced in June 2012. MRI-assisted adaptive treatment planning was carried out as per GEC-ESTRO recommendations. Retrospective data was collected using electronic medical records, histopathology, radiology and dosimetry reports. Treatment outcomes were calculated using the actuarial life table method from date of biopsy, except for late toxicities which were calculated from date of completion of ICBT. 1 patient was excluded from this analysis as size of tumour at diagnosis was not recorded in medical records. Results: Median age was 50 years (range 25-86). 70% had FIGO stage 2B disease and 50% of the patients had node positive disease. Median tumour size (T) was 43mm and 77% patients had tumour size 5cm or less. In this study median follow up was 26.7 months. Median overall treatment time was 47 days and mean EQD2 to HRCTV D90 was 88.2Gy. Median HRCTV volume was 26.6cm3. 7% showed primary treatment failure (5% to cervix alone and 2% to in-field nodal disease (pelvic or PA node) only. 11% subsequently relapsed (2% developed isolated PA nodal recurrence,
S93
6% developed distant disease only, 3% developed synchronous locoregional and distant recurrence). Continuous cervical control was 91%. Rate of local control for true pelvis was 91.4% in those achieving D90 O88Gy. Overall Survival (OS) for all patients was 56.7% [79.0% for node negative (N0) patients and 36.0% in node positive (N1)]. Cancer Specific Survival (CSS) for all patients was 63.0% (82.9% for N0 and 38.4% for N1). Progression Free Survival (PFS) for all patients was 74.1% (79.0% T- 5cm or less and 59.0% TO5cm, for 91.2% N0 and 54.7% for N1). Overall locoregional control rates (LRC) (cervix and pelvic nodes) were 87.0% for all patients. LRC was 90.2% (95.4% Te5cm or less and 88.2% TO5cm) for the patient cohort treated following the introduction of interstitial needles in June 2012 compared to 78.2% prior to this. Incidence of grade 3 GI/GU/vaginal toxicity was 8% of patients had with 0% at grade 4. The most prevalent toxicity was G1 vaginal toxicity affecting 46% of patients. Conclusions: Rates for CR, relapse and PFS in this study are consistent with existing single centre reports using similar protocols with EBRT and MRIassisted HDR-ICBT showing improved local control and a reduced toxicity profile compared to non-3D techniques. It also supports evidence that outcomes improve with increasing experience and with the introduction of interstitial needles. This study supports evidence that tumour size at diagnosis has a negative impact on LRC and PFS. Our rates of local control O90% in those achieving HRCTV D90 O88Gy10 are consistent with existing literature. Equally, nodal status has a negative impact on PFS, CSS and OS. This supports the importance of image-guided brachytherapy and the need for further investigation in the role of systemic chemotherapy in the upfront treatment of locally advanced, node positive cervical cancers to improve outcomes.
GSOR14 Presentation Time: 3:50 PM Outpatient Interstitial ImplantseIntegrating Cesium131 Permanent Interstitial Brachytherapy into Definitive Treatment for Gynecologic Malignancies Jonathan Feddock, MD, Prakash Aryal, PhD, Charles Wooten, MD, Marcus Randall, MD. Radiation Medicine, University of Kentucky, Lexington, KY, USA. Purpose: Curative intent brachytherapy for gynecologic cancers most often involves intracavitary approaches. In the less common clinical scenarios that require interstitial brachytherapy, template-guided after-loading techniques (e.g. Syed-Neblett interstitial implants) are generally used, yet patients might not be offered this option due to perceived risks or limitations in facilities, equipment, and expertise. Permanent Interstitial Brachytherapy (PIB) with Cs-131 in the outpatient setting is a relatively new procedure that expands brachytherapy options for women who might benefit from interstitial treatment. Our experience suggests that this option is exceptionally effective and safe in the curative management of selected gynecologic cancers for whom interstitial radiation techniques are indicated. Materials and Methods: Between August 2012 and November 2015, 22 patients received a total of 25 Cesium-131 PIB procedures at our institution as a component of definitive therapy for gynecologic malignancy following pelvic radiation therapy (PRT) with/without intracavitary brachytherapy (ICB). Paterson-Parker rules were used to calculate activity and seed distribution. Cumulative doses were calculated using Biological Effective Dose (BED) and Equivalent Dose at 2 Gy per fraction (EQD2) formalism. Results: Median follow up was 16 months (range 1.3-39.4). Primary diagnoses included Uterus (n512), Cervix (n52), and Vaginal (n510). Cell types included squamous cell (n57), endometrioid adenocarcinoma (n57), melanoma (n53), serous (n52), adenosquamous (n51), clear cell (n51), and small cell (n51). Histologic grades included grade 1 (n54), grade 2 (n58) and grade 3 (n510). Indications for interstitial brachytherapy were gross residual disease with thickness 0.5-1.5 cm (n512), positive surgical margin (n54), and inability to undergo a Syed-Neblett template implant due to medical co-morbidities (n56).