Low rates of androgen deprivation therapy use with salvage radiation therapy in patients with prostate cancer after radical prostatectomy

Abstract

Objective: The RTOG 9601 and GETUG-AFU 16 randomized controlled trials demonstrated that the addition of androgen deprivation therapy (ADT) to salvage radiation therapy (SRT) improves progression-free and, for RTOG 9601, overall survival. We examined national trends in the use of ADT with SRT.

Materials and methods: Of the 484,009 patients in the National Cancer Database from 2004 to 2012 with localized or locally advanced prostate cancer treated with radical prostatectomy (RP), 4,200 men received SRT (≥6mo after surgery). We used Pearson's chi-squared test to evaluate changes in ADT use, and multiple logistic regression to examine predictors of ADT use.

Results: Overall, 32.1% of SRT patients received ADT, which increased after initial results of RTOG 9601 showed an improvement in metastasis-free survival in 2010 (28.5% in 2008/2009 vs. 34.5% in 2011/2012, P = 0.006). Predictors of ADT use include presurgery prostate-specific antigen>20ng/ml vs.<10ng/ml (adjusted odds ratio [AOR] = 1.34, P = 0.002; 36.7% vs. 29.6%); positive vs. negative margins (AOR = 1.29, P = 0.001; 34.9% vs. 27.8%); Gleason 3+4 (AOR = 1.53; 21.3%), Gleason 4+3 (AOR = 2.40; 32.0%), or Gleason 8 to 10 (AOR = 4.49; 49.2%) vs. Gleason 2 to 6 (P≤0.005 for all; 13.2%); and pathologic T3a (AOR = 1.46; 30.9%), T3b (AOR = 2.50; 47.6%), or T4 (AOR = 4.14; 60.9%) vs. T2 (P<0.001 for all; 19.1%). Starting SRT 12 to 23.9 months (AOR = 0.69; 23.2%) or≥24 months (AOR = 0.25; 8.0%) after RP was associated with decreased odds of ADT use vs. starting SRT 6 to 8.9 months after RP (P≤0.002 for both; 35.0%).

Conclusion: Although less than one-third of SRT patients from the study era received ADT, there is evidence that physicians and patients have begun slowly adopting this practice with the 2010 reporting of a decrease in the cumulative incidence of metastases with the addition of ADT to SRT. Given the newly reported survival benefit of RTOG 9601, additional work will be necessary to identify which patients benefit the most from the use of ADT with SRT to individualize treatment.

Keywords: Androgen deprivation therapy; National Cancer Database; Practice patterns; Prostate cancer; Salvage radiation therapy.