Systematic Biopsy, Targeted Biopsy or a Combination—How Should We Detect Prostate Cancer in the Future?

Abstract

UNTIL now, ultrasound guided systematic prostate biopsy was the standard procedure for prostate cancer (PCa) detection. However, its limited ability in PCa discrimination resulting in over diagnosis of indolent tumors and under diagnosis of aggressive disease has opened the field for pre-biopsy prostate imaging. Magnetic resonance imaging (MRI) is likely the most sensitive imaging technique for the prostate. The implementation of validated scoring systems like the PI-RADS (Prostate Imaging Reporting and Data System) or the National Institutes of Health scoring system tends to improve decision making for prostate biopsy in daily clinical practice. Several recently published studies show promising sensitivity for prostate MRI to detect significant PCa compared to final pathology of prostatectomy specimens. For example, Bains et al recently reported that interobserver sensitivity and specificity of diffusion weighted MRI for the detection of significant PCa ranged from 89% to 91% and 77% to 81%, respectively. 1 In a study by Le et al the sensitivity of multiparametric MRI was 72% for the detection of high grade tumors and 80% for index lesions. 2 However, the same study clearly showed that MRI still has a limited ability to detect low risk PCa, resulting in an overall MRI sensitivity of 47% for the detection of all tumor foci in the prostatectomy specimen. Thus, from a clinical perspective a decision has to be made if the primary goal of prostate biopsy is to detect all forms of PCa or preferentially clinical significant cancers. Moreover we need a strategy to use systematic biopsies, targeted biopsies or a combination for PCa detection. In this issue of The Journal Radtke et al (page 87) contribute important information to these questions. 3 Using a well conducted prospective study design, the authors compared histopathological results of transperineal template saturation prostate biopsies vs MRI targeted biopsies with MRI/ultrasound fusion guidance in a large cohort. More Gleason score (GS) 7 or greater cancers were missed when using template saturation biopsies vs targeted biopsies (20.9% vs 12.8%), with a trend of superiority for MRI/ultrasound fusion targeted biopsies (p¼0.08). Additionally, fewer biopsy cores were needed to detect significant cancer when using targeted biopsies. Just 7.5% of all systematic cores detected GS 7 or greater cancer while 46% of targeted biopsy cores revealed GS 7 or greater disease. Thus, this study confirms the results of Pokorny et al, who showed that targeted biopsies improve the detection rate of GS 7 or greater cancer and reveal a higher proportion of positive cores compared to systematic biopsies (56.4% vs 15%). 4 Although the PI-RADS score offers valuable predictive information for the detection of clinically significant PCa, it still bears the risk of missing a certain number of these cancers. Radtke et al demonstrated that limiting biopsies to men with PI-RADS 3-5 would have missed 19.8% of all GS 7 or greater cancers. 3 Weagreethata combination ofsystematicbiopsies and targeted biopsies seems to be the safest approach for PCa detection. The combination of these techniques minimizes the risk of missing clinically significant PCa. Additionally, the detection of indolent cancers might allow MRI based active surveillance strategies as recently implemented in the PRIAS (Prostate Cancer Research International Active Surveillance) project. It is also important to note that a lethal clone might potentially also arise from a lower grade cancer focus in the primary tumor. 5 However, combination biopsy is actually not ready for daily clinical practice. Results from large prospective studies with adequate power are needed to validate the cohort studies published to date. Moreover, a standardized protocol for such a biopsy approach is needed as a variety of imaging protocols and biopsy techniques exist. An international consortium that formulated START (Standards of Reporting for MRI-targeted Biopsy Studies) of the prostate has made the first step in this direction. 6