Impact of age on treatment response in men with prostate cancer treated with radiotherapy.

Objective: To analyse the effect of age at diagnosis on clinical outcomes of localized prostate cancer (PCa) treated with radiation therapy. Subjects and methods: We identified 12 784 patients with intermediate- or high-risk localized PCa treated with radiation therapy (RT) and neoadjuvant androgen deprivation therapy (ADT) between 2000 and 2015 from nationwide Veterans Affairs data. Patients were grouped into three age categories (≤59, 60-69, and ≥70 years old). Outcomes included immediate PSA response (3-month post-RT PSA and 2-year PSA nadir, grouped into <0.10 ng/ml, 0.10-0.49 ng/ml, and ≥0.50 ng/ml), biochemical recurrence, and PCa-specific mortality. Multivariable regression models included ordinal logistic regression for short-term PSA outcomes, Cox regression for biochemical recurrence, and Fine-Gray competing risks regression for PCa-specific mortality. Results: A total of 2136 patients (17%) were ≤59 years old at diagnosis, 6107 (48%) were 60-69 years old, and 4541 (36%) were ≥70 years old. Median follow-up was 6.3 years. Younger age was associated with greater odds of higher 3-month PSA group (≤59 vs. ≥70: adjusted odds ratio [aOR] 1.90, 95% CI 1.64-2.20; p < 0.001) and higher 2-year PSA nadir group (≤59 vs. ≥70: aOR 1.89, 95% CI 1.62-2.19, p < 0.001). Younger age was associated with greater risk of biochemical recurrence (≤59 vs. ≥70: adjusted hazard ratio 1.45, 95% CI 1.26-1.67, p < 0.001) but not PCa-specific mortality (p = 0.16). Conclusion: In a large nationwide sample of US veterans treated with ADT and RT for localized PCa, younger age was associated with inferior short-term PSA response and higher risk of biochemical recurrence.