Incidence, Patterns, and Predictive Factors of Biochemical Failure Following Definitive Radiotherapy for Localized Prostate Cancer: A Retrospective Military Cohort Study.

BACKGROUND

Definitive radiotherapy represents a cornerstone treatment for localized prostate cancer, offering curative potential comparable to surgery. However, biochemical failure remains a concern, signaling possible disease progression.

OBJECTIVE

This study aimed to evaluate the frequency, timing, and predictors of biochemical failure in patients receiving definitive radiotherapy for localized prostate cancer at a military oncology center.

METHODS

We conducted a retrospective cohort study of 91 patients with localized or locally advanced prostate cancer (cT1-T3, N0-1, M0) treated with definitive radiotherapy at the Military Cancer Center in Jordan between 2020 and 2025. Biochemical failure was defined using the Phoenix criteria (prostate-specific antigen (PSA) nadir + 2 ng/mL). Biochemical recurrence-free survival was estimated using Kaplan-Meier analysis, and independent predictors of biochemical failure were identified using Cox proportional hazards regression.

RESULTS

The median age was 70 years, and the median pre-treatment PSA was 18.0 ng/mL. According to National Comprehensive Cancer Network (NCCN) risk stratification, 62/91 (68.1%) had high/very high-risk disease, 25/91 (27.5%) had intermediate-risk disease, and 4/91 (4.4%) had low-risk disease. Over a median follow-up of 36 months, 22 patients (24.2%) experienced biochemical failure, with a median time to failure of 24 months. The two-year and five-year biochemical recurrence-free survival rates were 84.6% and 70.3%, respectively. Multivariable analysis identified pre-treatment PSA greater than 20 ng/mL (hazard ratio (HR): 2.8; 95% confidence interval (CI): 1.4-5.6; p = 0.004) and PSA nadir greater than 0.1 ng/mL (HR: 3.2; 95% CI: 1.6-6.4; p = 0.001) as the strongest independent predictors of biochemical failure. Patients with PSA nadir > 0.1 ng/mL had a 3.2-fold higher hazard of biochemical failure compared to those with PSA nadir ≤ 0.1 ng/mL.

CONCLUSIONS

Definitive radiotherapy provides favorable biochemical control in this military cohort, with outcomes comparable to international benchmarks. Pre-treatment PSA and post-treatment PSA nadir independently predict biochemical failure, supporting their role in risk stratification and individualized follow-up planning. However, these findings require prospective validation in larger, multicenter cohorts before individualized surveillance strategies can be widely implemented.