Subtyping the Risk of Intermediate Risk Prostate Cancer for Active Surveillance Based on Adverse Pathology at Radical Prostatectomy

Abstract

Purpose: Intermediate risk prostate cancer is a heterogenous classification with favorable proposed criteria based on men treated with radiation therapy. However, there is uncertain application to active surveillance. We quantified the rate of adverse surgical pathology and implications for survival in patients at favorable intermediate risk compared to those with low risk prostate cancer.

Materials and methods: We performed a comparative cohort study of men with prostate cancer from 2009 to 2013 in the National Cancer Database who underwent radical prostatectomy. The study primary end point was adverse pathology, defined as Grade Group 3 or greater/pT3b/pN1. Various favorable intermediate risk definitions were evaluated, including the Memorial Sloan Kettering Cancer Center definition of Grade Group 2 or less with only 1 intermediate risk factor (Grade Group 2/cT2b/prostate specific antigen 10 to 20 ng/ml), which we defined as type 1 intermediate risk. The remaining patients at intermediate risk were classified as type 2 intermediate risk. Log binomial, logistic and Cox proportional hazards regression models were applied.

Results: Adverse pathological findings were noted in 3,519 of the 51,688 patients (6.8%) at low risk and 8,888 of the 42,720 Grade Group 2 patients (20.8%) at intermediate risk (RR 3.06, 95% CI 2.95-3.17, p <0.001). Stratification by prostate specific antigen and volume minimally impacted the absolute rate. Results were similar for the Memorial Sloan Kettering Cancer Center definition (type 1 intermediate risk). Type 2 intermediate risk led to a greater risk of adverse pathology (RR 8.52, 8.23-8.82, p <0.001) and Grade Group 1 intermediate risk led to lower risk (RR 2.00, 1.86-2.16, p <0.001). Patients at favorable intermediate risk had worse overall survival than patients at low risk in adjusted models due to adverse pathology.

Conclusions: Adverse pathology at radical prostatectomy was observed at a threefold higher rate in patients classified at favorable intermediate risk compared to low risk, leading to worse overall survival. Men at intermediate risk may be better classified as types 1 and 2 since none showed pathological outcomes similar to those of men at low risk.

Keywords: classification; mortality; pathology; prostatic neoplasms; risk factors; surgical.