Contrast-enhanced Gray-scale Transrectal Ultrasound-guided Prostate Biopsy in Men with Elevated Serum Prostate-specific Antigen Levels

Contrast-enhanced Gray-scale Transrectal Ultrasound-guided Prostate Biopsy in Men with Elevated Serum Prostate-specific Antigen Levels1 Jing Chun Yang, MD, Jie Tang, MD, Junlai Li, MD, Yukun Luo, MD, Yanmi Li, MD, Huaiyin Shi, MD

Rationale and Objectives. Our goal was to evaluate the role of contrast-enhanced gray-scale transrectal ultrasound (CETRUS)-guided prostate biopsy in patients with elevated serum prostate-specific antigen (PSA) levels. Materials and Methods. A total of 115 men (mean age, 70 years; range, 47⫺85) with serum PSA levels of greater than 4.0 ng/ml were assessed using gray-scale transrectal ultrasound (TRUS), power Doppler ultrasound (PDU), and CETRUS. Subsequently, these patients underwent systematic sextant transrectal biopsy and additional biopsies for positive sites on gray-scale TRUS, PDU, and CETRUS. The cancer detection rates of the three techniques were compared. Results. Cancer was detected in 63 of the 115 patients (55%). CETRUS was positive in 50 patients, 35 of whom (70%) had prostate cancer; CETRUS had a higher sensitivity, specificity, and accuracy of 65% (41/63), 83% (43/52), and 73% (84/115), respectively. CETRUS could have saved a significant number of patients from undergoing unnecessary biopsies, compared to TRUS and PDU. However, no significant correlation was found between the Gleason score and CETRUS grade. Conclusions. The use of CETRUS in detecting prostate cancer might reduce the number of unnecessary needle biopsies of the prostate in patients with abnormally high serum PSA levels and increase the detection rate of clinically significant prostate cancer. Key Words. Prostate cancer; transrectal ultrasound; contrast media; biopsy. ©

AUR, 2008

Prostate cancer is one of the most notable causes of death from cancer in men. The detection of prostate cancer is generally based on digital rectal examination (DRE) and transrectal ultrasound (TRUS) findings and serum prostate-specific antigen (PSA) determination (1,2). TRUS is the most commonly used imaging technique to guide the needle biopsy due to its excellent demonstration of zonal anatomy. However, multiple systematic random biopsies Acad Radiol 2008; 15:1291–1297 1

From the Departments of Ultrasound (J.C.Y., J.T., J.L., Y.L., Y.L.) and Pathology (H.S.), Chinese People’s Liberation Army General Hospital, 28 Fuxing Road, Beijing, 100853, P. R. China. Received February 17, 2008; accepted March 13, 2008. The financial support of the National Natural Science Foundation (grant 30772179) is gratefully acknowledged. Address correspondence to: J.T. e-mail: [email protected]

© AUR, 2008 doi:10.1016/j.acra.2008.03.022

have been shown to overlook a large number of clinically significant carcinomas. This fact has led to a dramatic increase in the number of biopsy samples taken for the detection of localized prostate cancer (3). There is an increasing need for improved diagnostic imaging to more accurately identify prostate cancer. Prostate cancer tissue is associated with increased microvessel density due to the proliferation of neovessels. Microvessels in malignant tissue are smaller than those of benign prostate tissue (4). The microvessels that proliferate in prostate cancer are below the resolution of conventional Doppler imaging; only the larger feeding vessels are visualized by this type of imaging (5). Microbubble contrast-enhanced ultrasound is an imaging technique used to dynamically detect tissue flow of both the macrovasculature and the microvasculature. Con-

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trast-enhanced ultrasound provides information on tissue perfusion, such that contrast-enhanced ultrasound may now play a role in liver mass characterization and the evaluation of masses in other solid viscera, similar to the role of contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) (6). In recent years, there has been an increasing focus on the application of contrast-enhanced ultrasound in prostate masses. Most published research on microbubble-enhanced imaging of the prostate has focused on developing a cost-effective strategy for improving the detection of prostate cancer (7,8). Preliminary studies suggest that the use of sonographic contrast agents enhances the visualization of neovascularity associated with prostatic cancer (9). The application of ultrasound contrast agents for the detection and clinical staging of prostate cancer is promising. The present study was designed to further investigate the clinical utility and limitations of contrast-enhanced transrectal ultrasound (CETRUS)⫺guided prostate biopsy in patients with elevated serum PSA levels.

MATERIALS AND METHODS Patients A total of 115 consecutive men (mean age, 70 years; range, 47⫺85) with serum PSA levels greater than 4.0 ng/ml (range, 4.3⫺387) were enrolled in this study between June 2006 and May 2007. Patients receiving treatment for prostatic disease or clinically apparent prostatitis were excluded from the study. Among them, 36 cases (31%) had serum PSA levels of 4.1 to 10.0 ng/ml. The study was approved by our local ethics committee. Written informed consent was obtained from every patient at enrollment. Also, prior to biopsy, the risks and benefits of the biopsy procedure were explained to each patient, and written informed consent was obtained. Contrast-Enhanced Transrectal Gray-scale Ultrasonography and Image Analysis All patients were examined with a 4- to 8-MHz EV8-C4 end-firing probe on a Sequoia 512S (Acuson, Sequoia 512 Encompass II; Siemens Medical Solutions, Mountain View, CA) using software version 10.0, which provides contrast pulse sequence (CPS) imaging. Gray-scale TRUS and PDU were performed in both transverse and sagittal planes at the fundamental frequency. Hypoechoic lesions in the peripheral zone on gray-scale TRUS were considered abnormal. The PDU

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gain was set at the level just below that at which background noise appeared. All PDU images were then prospectively analyzed, and the vascularity was judged according to the following grading system (0 to 2): 0, no abnormal accumulation; 1, intense focal accumulation; and 2, diffuse accumulation. Grades 1 and 2 were considered positive, and grade 0, negative. With bolus injection of contrast agent via a vein in the antecubital fossa and the imaging technique of CPS (with low acoustic power: mechanical index of 0.13), CETRUS was performed on all cases. The entire examination was recorded on the internal hard disk of the ultrasound machine and on CDs. The ultrasound contrast agent used in this study was SonoVue (BR1; Bracco, Milan, Italy). SonoVue is a suspension of stabilized sulfur hexafluoride (SF6) microbubbles in saline. Supplied as a lyophilized product in a septum-sealed vial, the agent was reconstituted by injecting 5.0 ml of saline through the septum, followed by hand agitation. The bubble concentration was in the range of 1 to 5 ⫻ 108 microbubbles/ml, with 90% of microbubbles less than 8 ␮m in diameter (10,11). A bolus of SonoVue (2.4 ml) was injected intravenously, followed by a 5-ml saline flush to ensure no residual contrast agent remained in the intravenous catheter. The enhancement patterns of the lesions were observed and categorized into four groups: 0, no enhancement; 1, no abnormal enhancement; 2, intense focal enhancement; and 3, diffuse enhancement. Grades 0 and 1 were considered negative, and grades 2 and 3, positive. All TRUS examinations and data analysis were performed by two experienced sonologists. Transrectal Ultrasound-guided Biopsy After gray-scale TRUS, PDU, and CETRUS examinations, transrectal biopsies under TRUS guidance were performed with an 18-gauge Tru-Cut needle powered by an automatic biopsy device (Bard Biopty Needles and Gun, Bard Urological Division, CR Bard, Covington, GA) subsequently at the same day. Two-core biopsies were taken from each hypoechoic and/or PDU-positive and/or CETRUS-positive site, followed by a systematic sextant biopsy (four samples from the peripheral zone and two from the transition zone). When the PDU or CETRUS showed a diffuse accumulation (grade 2) or enhancement pattern (grade 3), samples were obtained from the sites with the most intense signals or enhancement. Patients without any hypoechoic, PDU-positive, and CETRUS-positive le-

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Table 1 Relationship Between the Contrast-Enhanced Gray-Scale Transrectal Ultrasound (CETRUS) Grades and the Biopsy Results (n ⴝ 115)

Table 2 Relationship Between the Power Doppler Ultrasound (PDU) Grades and the Biopsy Results (n ⴝ 115) PDU Grade

CETRUS Grade Histologic Finding Cancer positive Gleason score 8⫺10 5⫺7 2⫺4 Subtotal Cancer negative BPH Inflammatory change PIN Subtotal Total (%)

0

1

2

Histologic Finding 3

0

1

2

Total (%)

10 16 1 27

8 21 0 29

3 4 0 7

21 41 1 63 (55)

32 2 0 34 61

7 3 2 12 41

1 5 0 6 13

40 8 2 52 (45) 115 (100)

Total (%)

3 4 1 8

7 7 0 14

12 22 0 34

3 4 0 7

25 37 1 63 (55)

32 2 0 34 42

7 1 1 9 23

4 3 1 8 42

0 1 0 1 8

43 7 2 52 (45) 115 (100)

BPH: benign prostatic hyperplasia; PIN: prostatic intraepithelial neoplasia.

sions underwent the sextant biopsy only. The tissue samples obtained from each site were submitted separately for pathologic analysis. Patients were prepared according to standard operating procedure for patients undergoing transrectal sonographically guided biopsy of the prostate. The use of aspirin or other anticoagulants was discontinued 1 week before the procedure. Antibiotic prophylaxis was orally administered (ofloxacin tablets, 300 mg) 1 hour before biopsy and continued for a total of six doses, taken twice daily. Statistical Analysis All statistical analyses were performed using SPSS 11.0 for Windows (SPSS Inc., Chicago, IL). The sensitivity and specificity of the three tests (gray-scale TRUS, PDU, and CETRUS) were analyzed by the ␹2 test. P values less than .05 were considered statistically significant.

RESULTS Prostate cancer was detected in 63 (55%) of the 115 men evaluated. Table 1 shows the relationship between the CETRUS grades and the biopsy results. Of the 115 men evaluated, 65 cases (57%) were defined as negative (grade 0 or 1) on CETRUS, and 42 (37%) and 23 (20%) were considered grades 0 and 1, respectively. Consequently, CETRUS-

Cancer positive Gleason score 8⫺10 5⫺7 2⫺4 Subtotal Cancer negative BPH Inflammatory change PIN Subtotal Total (%)

BPH: benign prostatic hyperplasia; PIN: prostatic intraepithelial neoplasia.

positive sites were identified in 50 cases (43%), including 41 malignant and 9 benign biopsy results, and 42 (36%) and 8 (7%) were considered grades 2 and 3, respectively. Table 2 shows the relationship between the PDU grades and the biopsy results. Of the 115 men evaluated, 61 cases (53%) were defined as negative (grade 0) on PDU. Consequently, PDU-positive sites were identified in 54 cases (47%), including 34 malignant and 20 benign biopsy results, and 41 (36%), and 13 (11%) were considered grades 1 and 2, respectively. Figure 1a shows representative gray-scale TRUS and CETRUS images of a patient found to have cancer by CETRUS-directed biopsies. No significant correlation was found between the Gleason score and CETRUS grade (P ⫽ .82; Table 1). Of nine false-positive cases, four (three with grade 2 and one with grade 3) had moderately inflammatory changes in the specimens; one patient had prostatic intraepithelial neoplasia (grade 2) (Fig 1b). Figure 2a shows representative gray-scale TRUS and PDU images of a patient found to have cancer by PDUdirected biopsies. No significant correlation was found between the Gleason score and PDU grade (P ⫽ .64; Table 2). Of 18 (12 with grade 1 and 6 with grade 2) falsepositive cases, 8 (3 with grade 1 and 5 five with grade 2) had moderately inflammatory changes in the specimens; 2 had PIN (grade 1) (Fig 2b).

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Figure 1. Contrast-enhanced ultrasound using cadence pulse sequencing technique shows that after a bolus injection of 2.4 ml SonoVue, there is a rapidly enhancing area (arrow). (a) Targeted biopsies revealed cancer with a Gleason score of 7. (b) Targeted biopsies revealed benign prostatic hyperplasia (BPH), partly with prostatic intraepithelial neoplasia II.

Of the 63 cancer cases, the CETRUS, PDU-directed, and systematic six-core biopsies independently detected 40, 34, and 35 cancer cases, respectively. Table 3 shows a comparison of the test performance among the three tests (gray-scale TRUS, PDU, and CETRUS). The overall sensitivity of CETRUS (n ⫽ 115) was 65%; specificity, 83%; positive predictive value, 82%; negative predictive value , 66%; and accuracy, 73%. The overall sensitivity of CETRUS was significantly higher than the value of 51% for TRUS (P ⬍ .05) (Fig 3). CETRUS also showed significantly higher specificity compared to the values of 58% for gray-scale TRUS and 65% for PDU (both P ⬍ .05). Of 36 cases with serum PSA levels of 4.1 to 10 ng/ml, cancer was found in 11 cases (31%) and CETRUS-positive lesions were identified in 10 cases (28%). Also in

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Figure 2. Power Doppler ultrasound shows a hypervascular area (arrow). (a) Targeted biopsies revealed cancer with a Gleason score of 7. (b) Targeted biopsies revealed benign prostatic hyperplasia.

the cases with serum PSA levels of 4.1 to 10 ng/ml, the CETRUS-directed biopsy appeared to have a superior combination of the test performance characteristics (sensitivity, 55%; specificity, 84%; positive predictive value, 60%; negative predictive value, 81%; and accuracy, 75%) compared to that of gray-scale TRUS and PDU (Table 3). However, it did not reach statistical significance because of the small number of cases.

DISCUSSION The discovery of PSA almost two decades ago and its introduction into clinical practice have revolutionized the management of prostate cancer. PSA levels were used to trigger prostate biopsies; however, the frequency of posi-

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Table 3 Comparison of Test Performance for Prostate Cancer Detection Type of Directed Biopsy Overall (n ⫽ 115) Gray-scale TRUS PDU CETRUS Serum PSA 4.1–10 ng/ml (n ⫽ 36) Gray-scale TRUS PDU CETRUS

Sensitivity

Specificity

PPV

NPV

Accuracy

32/63 (51)* 36/63 (57) 41/63 (65)

30/52 (58)* 34/52 (65)* 43/52 (83)

32/54 (59) 36/54 (67) 41/50 (82)

30/61 (49) 34/61 (56) 43/65 (66)

62/115 (54) 70/115 (61) 84/115 (73)

4/11 (36) 5/11 (45) 6/11 (55)

14/25 (56) 16/25 (64) 21/25 (84)

4/15 (27) 5/14 (36) 6/10 (60)

14/21 (67) 16/22 (73) 21/26 (81)

18/36 (50) 21/36 (58) 27/36 (75)

CETRUS: contrast-enhanced transrectal ultrasound; NPV: negative predictive value; PSA: prostate-specific antigen; PDU: power Doppler ultrasound; PPV: positive predictive value; TRUS: transrectal ultrasound. Data in parentheses are percentages. Sensitivity and specificity of gray-scale TRUS and PDU were compared with those of CETRUS using the ␹2 test. *p ⬍ .05.

tive biopsies for prostate cancer remains low in men with serum PSA levels of 4.1 to 10 ng/ml, and 70% of them undergo unnecessary biopsy (12). Although PDU has been reported to be promising for improving the positive biopsy rate in prostate cancer detection, a recent study has shown that Doppler ultrasound is operator dependent and examiner experience affects evaluation of the Doppler signal (13). Also, information on the slowly flowing blood at the capillary level has not previously been available on state-of-the-art Doppler. This type of technology has its limitations when it comes to details of organ perfusion or microcirculation (14,15). In this present study, PDU has a low sensitivity and specificity to detect prostate cancer in men with elevated serum PSA levels. Microbubble contrast-enhanced ultrasound is an imaging technique used to dynamically detect tissue flow of both the macrovasculature and microvasculature. Two basic ultrasound technologies are available to image microbubble contrast agents: Doppler and gray-scale harmonic imaging. Color power Doppler imaging and PCI, techniques that are available on most modern ultrasound systems, use relatively high energy levels that destroy a large proportion of the microbubbles as they are imaged. An intense Doppler signal is generated as the microbubbles burst during the Doppler imaging. Our previous study showed that contrast-enhanced Doppler ultrasound can effectively reveal the change in tumor vascularity during angiogenesis inhibitive therapy in prostate carcinoma (16). Presently, gray-scale harmonic imaging is a technologic advance that permits low-energy gray-scale imaging of contrast agents. Contrast-enhanced imaging

with color or power Doppler demonstrates flow primarily in larger feeding vessels, as most microbubbles are destroyed by the process of Doppler imaging before they reach the neovasculature. Contrast-enhanced gray-scale harmonic imaging demonstrates parenchymal enhancement based on imaging of microbubbles that travel into the microcirculation. To further improve the survival of microbubbles in the circulation, harmonic gray-scale imaging can be used with a reduced mechanical index or in an intermittent imaging mode. Intermittent imaging uses a reduced frame rate to lower the energy deposition into tissue, improve the survival time of microbubble contrast, and increase the parenchymal enhancement provided by ultrasound contrast agents. Harmonic gray-scale has several additional advantages over color and power Doppler, including superior spatial and temporal resolution and no blooming of the harmonic gray-scale enhancement around a vessel, in contrast to intense blooming with color or power Doppler imaging (5). In this present study, we used CETRUS with the CPS imaging technique, because this method was based on the processing of nonlinearly generated signals in the fundamental frequency band that can improve sensitivity and specificity to contrast agents; the presence and absence of perfusion can be determined objectively (17). A low mechanical index was also used to improve the survival of microbubbles in the circulation and increase the parenchymal enhancement provided by ultrasound contrast agents. Our results showed that the diagnostic specificity of CETRUS was higher than those of TRUS and PDU, which agreed with the results reported in previous studies (8,9,18).

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Figure 3. Transrectal ultrasound shows a hypoechoic lesion (arrow). (a) Targeted biopsies revealed at Gleason 8 Cancer. (b) Targeted biopsies revealed at BPH.

In prostate cancer detection terms, it is now the responsibility of radiologists to “protect” men from having biopsies by using new ultrasound techniques, which will avoid detecting clinically insignificant disease. Microbubble contrast-enhanced studies demonstrate a clear association between contrast enhancement in the prostate and the diagnosis of clinically significant cancer (5). Miyake et al. (19) reported that the combination of a biopsy Gleason score less than 7 and percent of positive biopsy core less than 15% might be useful as a predictor of insignificant disease; the further addition of serum PSA less than 10 ng/ml to these two parameters failed to enhance the predictive value of cancer significance. Based on their findings, in this present work, of the 41 CETRUS-positive cancer patients, only 3 (7%) had insignificant disease. The enhancement pattern of the lesions in these 3 patients was intense focal enhancement. It is indicated that clinically

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significant cancer will be detected more frequently by using biopsy cores targeted to areas of intense contrast enhancement. However, our results also showed that no significant correlation was found between the Gleason score and CETRUS grade. Of the 22 CETRUS-negative cancer patients, only 2 (9%) had insignificant disease. If only CETRUS-positive lesions were targeted for biopsy, 20 of 58 (34%) patients with significant cancer with negative enhancement pattern will be missed. Arger et al. (20) reported that focal hypervascular hypoechoic areas did not increase the likelihood of cancer. Some authors reported that high-grade tumors tended to display increased angiogenesis; however, there was no statistically significant association between histologic grade and angiogenesis (21,22). To some extent, their findings may support our results. A study showed that the lesions detected by contrast enhancement generally had a higher Gleason score (18). In this present study, there was no significant difference between PDU and CETRUS for detection of prostate cancer with higher Gleason scores. Also, the diagnostic sensitivity and specificity of TRUS, PDU, and CETRUS were lower in this present study than those in previous studies. We surmised that possibly the experience of the examiner continues to play a significant role, even with the latest technology (3). The limitation of this present study was that prostate cancer diagnosis and histologic grade were confirmed using TRUS-guided needle core biopsy. As we know, the gold standard sampling methods are to obtain large tissue samples from open prostatectomy or autopsy for histologic diagnosis of the prostate. Currently, additional studies are being done with an emphasis on obtaining samples from open prostatectomy to further confirm the findings.

CONCLUSION The use of CETRUS in detecting prostate cancer may reduce the number of unnecessary needle biopsies of the prostate in patients with abnormally high serum PSA levels and increase the detection rate of clinically significant prostate cancer. REFERENCES 1. Catalona WJ, Richie JP, Ahman FR. A multicenter evaluation of PSA and digital rectal examination (DRE) for early detection of prostate cancer in 6,371 volunteers. J Urol 1993; 149:412– 421.

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2. Cooper WH, Mosley BR, Rutherford CT. Prostate cancer detection in a clinical urological practice by ultrasonography, digital rectal examination and prostate specific antigen. J Urol 1990; 143:1146 –1154. 3. Loch T. Urologic imaging for localized prostate cancer in 2007. World J Urol 2007; 25:121–129. 4. Louvar E, Littrup PJ, Goldstein A, Yu L, Sakr W, Grignon D. Correlation of color flow in the prostate with tissue microvascularity. Cancer 1998; 83:135–140. 5. Halpern EJ. Contrast-enhanced ultrasound imaging of prostate cancer. Rev Urol 2006; 8(suppl 1):29 –37. 6. Wilson SR, Burns PN. Microbubble contrast for radiological imaging: 2. Applications. Ultrasound Q 2006; 22:15–18. 7. Sedelaar JP, van Leenders GJ, Hulsbergen-van de Kaa CA, et al. Microvessel density: Correlation between contrast ultrasonography and histology of prostate cancer. Eur Urol 2001; 40:285–293. 8. Halpern EJ, McCue PA, Aksnes AK, Hagen EK, Frauscher F, Gomella LG. Contrast-enhanced US of the prostate with Sonazoid: Comparison with whole-mount prostatectomy specimens in 12 patients. Radiology 2002; 222:361–366. 9. Halpern EJ, Verkh L, Forsberg F, Gomella LG, Mattrey RF, Goldberg BB. Initial experience with contrast-enhanced sonography of the prostate. AJR Am J Roentgenol 2000; 174:1575–1580. 10. Schneider M, Arditi M, Barrau MB, et al. BR1: A new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles. Invest Radiol 1995; 30:451– 457. 11. Kaps M, Legemate DA, Ries F, et al. SonoVue in transcranial Doppler investigations of the cerebral arteries. J Neuroimaging 2001; 11:261– 267. 12. Catalona WJ, Ramos CG, Carvalhal GF, Yan Y. Lowering PSA cutoffs to enhance detection of curable prostate cancer. Urology 2000; 55: 791–795.

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13. Halpern EJ, Strup SE. Using gray-scale and color and power Doppler sonography to detect prostatic cancer. AJR Am J Roentgenol 2000; 174:623– 627. 14. Halpern EJ, Frauscher F, Rosenberg M, Gomella LG. Directed biopsy during contrast-enhanced sonography of the prostate. AJR Am J Roentgenol 2002; 178:915–919. 15. Strohmeyer D, Frauscher F, Klauser A, et al. Contrast-enhanced transrectal color Doppler ultrasonography (TRCDUS) for assessment of angiogenesis in prostate cancer. Anticancer Res 2001; 21:2907–2913. 16. Tang J, Li S, Li J, et al. Evaluation of the effect of protamine on human prostate carcinoma PC-3m using contrast enhanced Doppler ultrasound. J Urol 2003; 170:611– 614. 17. Phillips PJ. Contrast pulse sequences (CPS): Imaging nonlinear microbubbles. Ultrasonics Symp 2001; 2:1739 –1745. 18. Halpern EJ, Rosenberg M, Gomella LG. Prostate cancer: Contrast-enhanced US for detection. Radiology 2001; 219:219 –225. 19. Miyake H, Sakai I, Harada K, Hara I, Eto H. Prediction of potentially insignificant prostate cancer in men undergoing radical prostatectomy for clinically organ-confined disease. Int J Urol 2005; 12:270 –274. 20. Arger PH, Malkowicz SB, VanArsdalen KN, Sehgal CM, Holzer A, Schultz SM. Color and power Doppler sonography in the diagnosis of prostate cancer: Comparison between vascular density and total vascularity. J Ultrasound Med 2004; 23:623– 630. 21. Rubin MA, Buyyounouski M, Bagiella E, et al. Microvessel density in prostate cancer: Lack of correlation with tumor grade, pathologic stage, and clinical outcome. Urology 1999; 53:542–547. 22. Papadopoulos I, Sivridis E, Giatromanolaki A, Koukourakis MI. Tumor angiogenesis is associated with MUC1 overexpression and loss of prostate-specific antigen expression in prostate cancer. Clin Cancer Res 2001; 7:1533–1538.

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