Salvage prostatectomy for post-radiation adenocarcinoma with treatment effect: Pathological and oncological outcomes

Introduction: Prostate biopsies following localized radiation therapy for prostate cancer often demonstrate residual prostatic carcinoma with treatment effect (CTE). The final oncological outcome of prostatic CTE is currently uncertain. We studied the pathological and oncological outcomes for a large cohort of patients who had CTE on post-radiation therapy biopsy and subsequently underwent salvage radical prostatectomy (SRP). Methods: A single-centre retrospective review of all SRPs performed from 1995-2014 was performed. Cases were selected for this analysis if they had had a post-radiation "for-cause" biopsy. Biopsy results were compared to final pathology results following SRP. Pathological and clinical outcomes were compared by extent of treatment effect seen on the post-radiation biopsy. Results: A total of 70 patients who had salvage prostatectomy at MD Anderson Cancer Centre from 2007-2015 met study criteria. CTE was found on biopsy in the absence of other adenocarcinoma in 16 patients. Among them, one (7%) patient had no evidence of carcinoma at the time of salvage prostatectomy, four (27%) had CTE, three (20%) had adenocarcinoma with minimal or partial treatment effect (PTE), and seven (47%) had adenocarcinoma with no treatment effect (NTE). For those with CTE on biopsy, 69% had biochemical recurrence at a median time of 0.4 years (interquartile range [IQR] 0.22-1.52) vs. 52% for all patients (median 0.44 years, IQR 0.11-1.70) and 47% for those with no treatment effect (median 0.62 years, IQR 0.05-1.90). Metastasis developed after salvage prostatectomy in 11.8% of the whole cohort (8/68, median time to metastasis was 3.03 years, IQR 2.45-4.47), 26.7% of patients with CTE (median 3.2 years, IQR 1.96-4.44), and 6.7% of patients with NTE (median 2.45 years, IQR 0.98-2.86). Median recurrence-free survival was 2.78 years (95% confidence interval [CI] 0.84-5.43) for all patients, 0.51 years (95% CI 0.22-2.35) for those with CTE, and 4.95 years (95% CI 0.95-7.08) for those with NTE; the difference was not significant (p=0.13). On multivariate analysis, pre-SRP biopsy Gleason grade <7 (hazard ratio [HR] 0.38; 95% CI 0.14-1.02) and number of biopsy cores positive for carcinoma (HR 1.11; 95% CI 1.00-1.22) were significant for prediction of cancer recurrence. Conclusions: Patients undergoing salvage prostatectomy for CTE or PTE demonstrated in a for-cause biopsy after radiation therapy had pathological evidence of viable, untreated cancer in more than 50% of cases and were at significant risk of adverse pathological features. Patients with CTE may therefore benefit from salvage radical prostatectomy. Our study is limited by its retrospective nature and sample size. More studies are required to further validate our findings and assess the benefit of SRP in this population.