Adjuvant Radiotherapy Improves Survival in Select Patients with Prostate Cancer

Adjuvant radiotherapy was associated with improvements in overall survival (OS) in patients with prostate cancer who had Gleason scores of 8 to 10, a total of 32 positive lymph nodes, or negative surgical margins, according to research findings presented by Christian Schaufler, MD, of the University of Connecticut School of Medicine, at the 2022 American Urological Association Annual Meeting.

Dr. Schaufler and colleagues noted that the optimal management of node-positive (pN1) prostate cancer after radical prostatectomy has not yet been made clear. Additionally, the researchers indicate that the use of immediate, life-long androgen deprivation therapy (ADT) remains suboptimal, despite randomized evidence supporting this approach. Additionally, Dr. Schaufler and colleagues stated that recent research evaluating early salvage radiotherapy has only evaluated this strategy in a minority of patients with pN1 prostate cancer.

These research limitations led Dr. Schaufler and researchers to evaluate a hypothetical pragmatic trial consisting of immediate, adjuvant radiotherapy compared with observation in patients with pN1 prostate cancer.

The investigators used RADICALS-RT to inform the design of the target trial. Men between the ages of 50 and 69 years with pT2-3 Rany pN1 M0, pre-treatment prostate-specific antigen <50 ng/mL prostate cancer were identified in the NCDB from 2006 and 2015. These patients received 60 to 72 Gy of adjuvant radiotherapy with or without ADT within 26 weeks of radical prostatectomy or observation.

In total, the cohort included 3510 patients, including 587 (17%) who received adjuvant radiotherapy. Approximately 73% of patients who received adjuvant radiotherapy also received concurrent ADT.

Over the median follow-up period of 42.3 months, a total of 333 deaths were reported. Baseline characteristics were balanced following stabilized inverse probability of treatment re-weighting. The adjusted OS was 94% compared with 89% at 5 years and 82% vs 80% at 8 years for adjuvant radiotherapy vs observation, respectively (p=0.12).

According to inverse probability of treatment reweighted Cox regression modeling, adjuvant radiotherapy was associated with a lower risk of all-cause mortality compared with observation, but the difference between the approaches was not statistically significant (hazard ratio [HR] = 0.71, p=0.06).

Analyses which examined the heterogeneity of treatment effects found that adjuvant radiotherapy was significantly associated with improvements in OS in men with Gleason scores of 8 to 10 disease (HR=0.59, p=0.01), ³2 positive lymph nodes (HR=0.50, p=0.04 for 2 positive LNs; HR=0.43, p=0.01 for ³3 positive LNs), or negative surgical margins (HR=0.50, p=0.03).