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

PURPOSE: 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).

METHODS AND MATERIALS: 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.

RESULTS: 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).

CONCLUSION: 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.