Observation with or without late radiotherapy is equivalent to early radiotherapy in high-risk prostate cancer after radical prostatectomy: A SEER-Medicare analysis on trends, survival outcomes, and complications

Background: We aimed to illustrate national trends of post-radical prostatectomy (RP) radiotherapy (RT) and compare outcomes and toxicities in patients receiving eRT versus observation with or without late radiotherapy (lRT). Methods: Utilizing the Surveillance, Epidemiology, and End Results (SEER)-Medicare data from 2001 to 2011, we identified 7557 patients with high-risk pathologic features after RP (≥pT3N0 and/or positive surgical margins). Our study cohort consisted of patients receiving RT within 6 months of surgery (eRT), those receiving RT after 6 months (lRT), and those never receiving RT (observation). Another subcohort, delayed RT (dRT), encompassed both lRT and observation. Trends of post-RP RT were compared using the Cochran–Armitage trend test. Cox regression models identified factors predictive of worse survival outcomes. Kaplan–Meier analyses compared the eRT and the dRT groups. Results: Among those with pathologically confirmed high-risk prostate cancer (PCa) after RP, 12.7% (n = 959), 13.2% (n = 1710), and 74.1% (n = 4888) underwent eRT, lRT, and observation without RT, respectively. Of these strategies, the proportion of men on observation without RT increased significantly over time (p = 0.004). The multivariable Cox regression model demonstrated similar outcomes between the eRT and the dRT groups. At a median follow-up of 5.9 years, five-year overall and cancer-specific survival outcomes were more favorable in the dRT group, when compared to the eRT group. Conclusions: A blanket adoption of the eRT in high-risk PCa based on clinical trials with limited follow-up may result in overtreatment of a significant number of men and expose them to unnecessary radiation toxicity.