Is immediate adjuvant radiotherapy necessary for men with positive surgical margin after robotic-assisted radical prostatectomy?

Background: The role of immediate adjuvant radiotherapy (ART) in the management of positive surgical margin (PSM) following radical prostatectomy (RP) for low-grade prostate cancer (PCa) remains unclear. We aim to investigate our experience on survival outcome between immediate ART versus active surveillance in PSM groups after robotic-assisted RP (RaRP). Materials and Methods: The PSM cohort was divided into an adjuvant therapy group, consisting of immediate radiotherapy (RT) with or without androgen deprivation therapy (ADT) within six months after surgery, and observation group, consisting of close follow-up at the out-patient clinic. Salvage therapy was conducted using RT with/without ADT if biochemical recurrence (BCR) occurred (PSA level >0.2 ng/mL) during follow-up. 461 patients with PCa who underwent RaRP between December 2006 and June 2014 were included. Data of patients with PSM (n = 79) were extracted and followed up to June 2020. We aimed to compare the outcomes of immediate ART against observation or salvage RT in patients with PSM. Hence, we focused on those who had a PSA level <0.2 ng/mL after RaRP. Those with a PSA level >0.2 ng/mL were excluded. Results: No significant differences in age or preoperative PSA levels were observed after stratification to immediate ART and observation groups. Three patients (5.6%) received immediate ART with/without ADT. Another 51 patients received active surveillance, of which 18 (35.3%) received salvage ART with/without ADT due to BCR (PSA ≥0.2 ng/mL). There was no significant difference between immediate ART and observation groups in 5-year BCR-free survival (P = 0.072), local recurrence-free survival (P = 0.490), distant metastasis-free survival (P = 0.225), and overall survival (P = 0.517). Conclusion: Of the RaRP patients with PSM in the Asian population, we discovered that immediate ART following RaRP may not offer a significant advantage to active surveillance. Routine monitor of PSA levels had shown equally successful disease control. Salvage ART could be used on detection of BCR.