The impact of comorbidities on the benefits of prolonged androgen ablation in patients with T3-4 prostate cancer treated with external beam radiation therapy.

Abstract

To determine whether the survival benefit associated with prolonged androgen deprivation therapy (ADT) and radiotherapy (EBRT) varies with baseline estimates of overall survival in cT3-4 prostate cancer patients (PCa). In 1997, the BC Cancer Agency adopted as standard a policy of prolonged ADT (>18months) with EBRT for locally advanced PCa. Two cohorts of cT3-T4 PCa treated with EBRT were selected: 1993-1995 (early: N=725) and 1999-2001 (late: N=584). Duration of ADT and baseline prognostic factors (age, clinical stage, grade, presenting PSA, and Charlson index (CCI)) were abstracted from charts. Estimates of 10-year (E10) survival using an age-adjusted CCI were calculated and patients were grouped into low (<60%), medium (60-90%) and high (>90%) E10. In each E10 group, actual overall survivals were compared by era using log rank test. There were 318 low, 544 medium, and 447 high E10 patients with median follow-up of 11.1years. Gleason grade and T stage were not statistically different between E10 groups. As expected, median age and baseline CCI were higher in lower E10 groups (p<0.0001). Overall survival was higher in the late era, but varied with E10 group: low (43% vs. 49%, p=0.54), medium (55% vs. 64%, p=0.02) and high (66% vs. 77%, p=0.01). The policy of prolonged ADT with EBRT provides a survival benefit that varies with baseline risk of death from other causes. Absolute benefit from ADT is largest in those with medium or high E10.