Long-term biopsy outcomes in prostate cancer patients treated with external beam radiotherapy: a systematic review and meta-analysis

Abstract

Abstract Background Biopsy after external beam radiotherapy (EBRT) for localised prostate cancer (PCa) is an infrequently used but potentially valuable technique to evaluate local recurrence and predict long-term outcomes. Methods We performed a meta-analysis of studies until March 2020 where a post-EBRT biopsy was performed on patients with low-to intermediate risk PCa, according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. The primary outcome was the aggregate post-EBRT positive biopsy rate (≥2 years after EBRT) and the associated odds ratio (OR) of a positive biopsy on biochemical failure (BCF), distant metastasis-free survival (DMFS) and prostate cancer-specific mortality (PCSM). A sensitivity analysis was performed which examined biopsy rate as a function of post-EBRT biopsy protocol, PCa risk, ADT usage and radiation dose. Results A total of 22 studies were included, of which 10 were randomised controlled trials and 12 were cohort studies. Nine out of the 22 studies used dosing regimens consistent with the 2020 NCCN radiotherapy guidelines. The weighted-average positive biopsy rate across all 22 studies was 32% (95%-CI: 25–39%, n = 3017). In studies where post-treatment biopsy was part of the study protocol, the rate was 35% (95%-CI: 21–38%, n = 2450). In the subgroup of studies that conformed to the 2020 NCCN radiotherapy guidelines, this rate was 22% (95% CI: 19–41%, n = 832). Patients with positive biopsy had a 10-fold higher odds of developing BCF (OR of 10.3, 95%-CI: 3.7–28.7, p < 0.00001), 3-fold higher odds of developing distant metastasis (OR 3.1, 95%-CI: 2.1–4.7, p < 0.00001) and 5-fold higher odds of dying from their PCa (OR 5.1, 95%-CI: 2.6–10, p < 0.00001). Conclusion A positive biopsy after EBRT is associated with a poor prognosis compared to a negative biopsy. The post-EBRT positive biopsy rate is an important measure which provides additional insight when comparing EBRT to other treatment modalities for PCa.