The impact of the duration of adjuvant hormonal therapy in patients with unfavorable prognosis prostate cancer treated with radiotherapy: Secondary analysis of RTOG 85–31

Abstract

5062 Background: RTOG 85–31 was a Phase III trial of androgen suppression for life as an adjuvant to radiotherapy. However not all patients continued on the protocol-mandated long-term hormonal therapy despite no evidence of recurrent disease. This analysis correlates duration of adjuvant hormonal therapy and outcomes among patients who prematurely discontinued long-term hormonal therapy. Methods: The protocol mandated pelvic radiotherapy (60–66 Gy) followed by goserelin 3.6 mg monthly given indefinitely or until disease progression. To avoid potential bias due to early progression/death, only patients who were alive with no evidence of disease at the time of cessation of hormonal therapy were included. There were 377 analyzable patients. Patients were divided in groups based on the hormonal therapy duration (HTD), as follows: = 1 year (27.3%), 1< and =2 years (11.4%), 2< and =4 years (13.3%), 4< and =6 years (10.6%) and > 6 years (37.4%). End-points were overall survival, disease-free survival, disease-free survival with PSA <1.5 ng/mL, disease-specific survival, local failure and distant failure. Cox-proportional hazards regression model was used to test the outcomes among the 5 groups. Results: The median follow-up time of surviving patients is 11.27 years. Pretreatment characteristics by hormone duration groups were well balanced except for age. The median duration of adjuvant hormonal therapy was 3.59 years. For each outcome, there are statistically significant differences among the 5 HTD groups in all outcomes without adjusting for other covariates. Pairwise comparisons show that HTD > 6 year group is significantly associated with having an improved survival and fewer failure events than all other HTD groups (HR < 1, p-value <0.0001). Adjusted for age and stratification variables, the HTD>6 year group remains the only group significantly associated with having fewer failure events in all outcomes. Conclusions: Prolonged HTD of > 6 years is significantly associated with improvements in all end-points studied. Based on these data, decreasing HTD to < 6 years may have a detrimental effect in patients with unfavorable prostate cancer. No significant financial relationships to disclose.