Objective: To determine oncological outcomes between adjuvant and salvage radiotherapy after radical prostatectomy for prostate cancer in Siriraj Hospital.
Material and Method: All record forms of patients with prostate cancer who underwent radiotherapy after radical prostatectomy in Siriraj Hospital between 2006 and 2014 were reviewed. Data of demographic information, perioperative findings, pathological reports, biochemical recurrence and metastasis-free survival were evaluated.
Results: All of 151 patients with adverse pathological features, there were extra-capsular extension 76%, seminal vesicles
invasions 36% and positive margins 75%. Patients with localized, locally advanced disease, and lymph nodes involvement were 16.5%, 76.2% and 7.3% respectively. Sixty-one patients had Gleason score 8 to 10. Sixty percent had concomitant androgen deprivation therapy. Mean duration from surgery to radiotherapy was 11 months with mean cumulative radiation dose was 66 Gy. Median follow-up time was 53 months (range 8 to 117 months). Overall 5-year biochemical recurrence-free survival was 53.1% and 5-year metastasis-free survival was 90.8%. Patients with early adjuvant radiotherapy after surgery within five months showed better biochemical recurrence-free survival compare to surgery alone (70.9% vs. 18.4%; p<0.001) with adjusted hazard ratio = 4.78 (95% CI, 2.80 to 8.09) but no statistical significance when compared to patients with salvage radiotherapy (78.7% vs. 69.1%; p = 0.114). Metastasis-free survival showed no difference between two settings (100% vs. 90.6%; p = 0.05). The incidence of late gastrointestinal and genitourinary toxicities grade 3 to 4 were 5.8% and 10.8%, respectively.
Conclusion: Radiotherapy after radical prostatectomy is effective treatment for patients with adverse pathological features. Our study demonstrated that adjuvant radiotherapy can improve biochemical recurrence-free survival and metastasis-free survival.

Keywords: Prostate cancer, Adjuvant radiotherapy after prostatectomy, Biochemical recurrence-free survival and metastasisfree survival