(P064) Outcomes After Adjuvant Radiation Therapy for Prostate Cancer at a Comprehensive Cancer Center

April 30, 2015

At a comprehensive cancer center, men who are referred for adjuvant RT often have margin involvement and/or ECE. Patients did well overall, with high 5- and 10-year freedom from failure. Only Gleason 8/9 disease was associated with increased failure after adjuvant RT.

Emma B. Holliday, Deborah A. Kuban, Lawrence Levy, Priya Master, Seungtaek Choi, Steven J. Frank, Andrew K. Lee, Sean E. McGuire, Usama Mahmood, Thomas J. Pugh, Karen E. Hoffman; UT MD Anderson Cancer Center

BACKGROUND: Randomized trials have shown that adjuvant radiation therapy (RT) improves prostate cancer control for men with extracapsular extension (ECE), seminal vesicle (SV) involvement, and/or positive surgical margins (SMs) at the time of prostatectomy. We report cancer control outcomes for men who received adjuvant RT at a comprehensive cancer center.

METHODS: Men who received adjuvant RT within 12 months of prostatectomy from 1987 through 2010 were identified in an institutional database. All men had PSA < 0.2 ng/mL at the time of RT. Failure was defined as a rising postradiation PSA of 0.2 ng/mL; local, nodal, or distant recurrence; or the initiation of salvage treatment. Time to failure was calculated from the end of radiation treatment. Cox proportional hazards models evaluated the association between patient characteristics, tumor characteristics, radiation treatment, and cancer control. Kaplan-Meier product-limit estimator was used to estimate 5- and 10-year failure.

RESULTS: A total of 137 men received adjuvant RT. Median time from prostatectomy was 5.1 months (interquartile range [IQR]: 1.4–6.4 mo). Most men had positive SM (n = 127, 92.7%) and ECE (n = 98, 71.5%). A total of 38% had Gleason 8/9 disease (n = 52) at prostatectomy. Median radiation dose was 60 Gy (IQR: 60–66 Gy). Few men (n = 24, 17.5%) received concurrent hormone therapy (HT) with RT. Patients were more likely to receive HT if their prostatectomy was performed outside of the institution (P = .021) or if they had involved SV (P < .001). With a median follow-up of 11.4 years (IQR: 5.6–17.5 yr), 22 men failed. The 5-year failure for the entire cohort was 11.9%, and the 10-year failure was 16%. Gleason score was the only factor significantly associated with failure. The 5- and 10-year failure rates for men with Gleason 8/9 disease were 18.4% and 20.8%, respectively, while the 5- and 10-year failure rates for men with Gleason < 8 disease were 6.7% and 11.9%, respectively (P = .013). Radiation dose (< 66 Gy vs ≥ 66 Gy), surgical margin status, and receiving HT were not associated with failure. 

CONCLUSIONS: At a comprehensive cancer center, men who are referred for adjuvant RT often have margin involvement and/or ECE. Patients did well overall, with high 5- and 10-year freedom from failure. Only Gleason 8/9 disease was associated with increased failure after adjuvant RT. 

Proceedings of the 97th Annual Meeting of the American Radium Society- americanradiumsociety.org