The Outcome of Immediate Adjuvant Postoperative External Beam Radiotherapy Versus Observation Alone After Radical Prostatectomy in High-Risk Prostate Cancer: A Meta Analysis.

Background/Objectives: High-risk prostate cancer patients undergoing radical prostatectomy remain at significant risk of biochemical recurrence and metastasis. Immediate adjuvant external beam radiotherapy (EBRT) has been proposed to improve outcomes, but its role compared to observation remains debated due to potential toxicity and uncertain overall survival benefit. To evaluate the efficacy and safety of immediate adjuvant EBRT versus observation following radical prostatectomy in men with high-risk prostate cancer. Methods: A meta-analysis was conducted according to PRISMA guidelines. We sought to include both randomized controlled trials (RCTs) and observational studies published between 2005 and 2025; however, no observational studies meeting the predefined criteria were identified. Therefore, only RCTs comparing immediate adjuvant EBRT with observation in patients with adverse pathological features and undetectable postoperative PSA were included. Primary outcomes were biochemical recurrence-free survival (BCR-FS), metastasis-free survival (MFS), and overall survival (OS). Secondary outcomes included toxicity and quality of life (QoL). Data were pooled using Mantel-Haenszel and inverse variance methods, and heterogeneity was assessed with I2 statistics. Results: Four RCTs (n = 1987) met the inclusion criteria. Adjuvant EBRT significantly improved progression-free survival (PFS) (HR = 0.38; 95% CI: 0.20-0.74; p = 0.004) and metastasis-free survival (HR = 0.70; 95% CI: 0.54-0.92; p = 0.01). However, OS benefit was not statistically significant (HR = 0.88; 95% CI: 0.59-1.32; p = 0.55). Heterogeneity was substantial for some outcomes (I2 up to 71%). Adjuvant EBRT was associated with higher genitourinary and gastrointestinal toxicity compared to observation. Conclusions: Immediate adjuvant EBRT after radical prostatectomy improves PFS and MFS in high-risk prostate cancer but does not confer a clear OS advantage. Treatment decisions should be individualized, balancing disease-control benefits against toxicity risks. Observation with early salvage RT remains a reasonable alternative in selected patients.