Omission of Contralateral Systematic Biopsies in Unilateral Suspicious Prostate Cancer on Magnetic Resonance Imaging: Implications for Radiation Treatment Selection

Background and objective: A combined approach of magnetic resonance imaging (MRI) targeted biopsies (TBx) and systematic biopsies (SBx) was recommended previously in patients with unilateral suspicious prostate cancer (PCa) on MRI. Yet, new PCa guidelines suggest that contralateral SBx can be omitted. It is unknown how this guideline modification impacts treatment selection. This study evaluates the value of contralateral SBx in radiation treatment selection in patients with unilateral suspicious lesions (Prostate Imaging Reporting and Data System [PI-RADS] ≥3) on MRI. Methods: Case files of 80 patients with a unilateral suspicious lesion on diagnostic MRI who underwent TBx and bilateral SBx were collected. The cases were presented to four radiation oncologists twice: once with diagnostic information of bilateral SBx and TBx, and once with diagnostic information of ipsilateral SBx and TBx pathology results. Based on this information, external beam radiation treatment (EBRT) fractionation scheme, duration of androgen deprivation therapy (ADT), and feasibility of brachytherapy (monotherapy or brachyboost) were considered. Key findings and limitations: After omitting information of contralateral SBx pathology results, selection of EBRT fractionation scheme and ADT duration changed in 14% (95% confidence interval [CI] 9.8–17) and 15% (95% CI 11–19) of cases, respectively. The feasibility of brachytherapy as monotherapy and brachyboost, respectively, changed in 11% (95% CI 7.9–15) and in 21% (95% CI 17–26) of cases, with overall poor interobserver variability for both diagnostic scenarios (Fleiss’ kappa 0.15 and 0.16). Conclusions and clinical implications: Our findings indicate that omitting contralateral SBx has an impact on the treatment selection of patients who choose for radiation therapy as their treatment for locally confined PCa. Patient summary: In patients with prostate cancer identified via magnetic resonance imaging on one side of the prostate, exclusion of prostate biopsies from the opposite side affected the selection of radiation treatment.