Long-Term Implications of a Positive Post Treatment Biopsy Among Patients Treated with External Beam Radiotherapy for Clinically Localized Prostate Cancer.

To determine the prognostic importance of a positive post-treatment biopsy after prostate radiotherapy.

382 patients underwent a post-treatment biopsy after external beam radiotherapy (EBRT) for clinically localized prostate cancer. Post-treatment biopsies were classified as positive (prostatic adenocarcinoma without typical radiation-induced changes), negative (no evidence of carcinoma) or adenocarcinoma with severe treatment effect (STE). The median follow-up in survivors was 9 years. Competing risks regression was used to assess relationship between prognostic predictors and CSM, DM, and PSA failure.

The prevalence of a positive, treatment effect and negative biopsy were 30%, 22% and 48%, respectively. Omission of androgen deprivation therapy and high-risk disease were associated with a 2.6 and 1.8-fold increase in odds of positive post-treatment biopsy, respectively. The 15-year PSA-relapse rates for negative, STE and positive post-treatment biopsy patients were 34%, 36% and 79%, respectively (p< 0.001). After controlling for known predictors, the hazard of distant metastases was 2.6-fold higher for positive biopsy patients (p<0.001) and cause-specific mortality was twice as high (HR: 2.00, p=0.022) in those with positive biopsy as compared to patients with negative and STE biopsy outcomes.

A positive post-treatment biopsy after EBRT was associated with a higher hazard of distant metastases and prostate cancer related death. Patients with STE- classified biopsies have biologic characteristics more like those with a negative biopsy compared to a positive biopsy. Post-treatment biopsies were more often positive in the setting of EBRT alone without ADT or in the presence of high-risk disease.

The Journal of urology. 2019 Feb 05 [Epub ahead of print]

Michael J Zelefsky, Debra A Goldman, Victor Reuter, Marisa Kollmeier, Sean McBride, Zhigang Zhang, Melissa Varghese, Xin Pei, Zvi Fuks

From the Department of Radiation Oncology, Department of Pathology, Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, 1275 York Ave, N,Y., N.Y. 10065.