BACKGROUND: Although radiotherapy (RT) provides potential benefits for patients with hepatocellular carcinomas (HCCs) that are unsuitable for operation, the specific role of adjuvant RT in HCC after hepatectomy remains ill defined. The current study's aim was to evaluate the safety and efficacy of adjuvant RT for centrally located HCCs after narrow-margin (<1 cm) hepatectomy. STUDY DESIGN: The study included 119 patients with centrally located HCCs who underwent narrow-margin hepatectomy between July 2007 and March 2012. Patients were prospectively randomized to receive adjuvant RT (n = 58) or were assigned to a control group (n = 61). Surgical outcomes, safety, and survival rates were evaluated. RESULTS: Hepatectomy was successfully performed in all patients. No cases of radiation-induced liver disease were observed. One-, 3-, and 5-year recurrence-free survival rates were 78.1%, 56.5%, and 36.9% in the adjuvant RT group and 72.4%, 40.1%, and 16.0% in the control group, respectively (p = 0.06, log-rank test). Corresponding overall survival rates were 96.2%, 72.6%, 48.4%, and 89.6%, 74.5%, 37.2%, respectively (p = 0.48, log-rank test). One-, 3-, and 5-year recurrence-free survival rates in patients with small-diameter tumors (<= 5 cm) were 88.8%, 67.4%, 42.9% in the adjuvant RT group and 82.3%, 42.9%, 21.5% in the control group (p = 0.03, log-rank test). Corresponding overall survival rates were 97.5%, 75.3%, 75.3%, and 94.7%, 84.1%, 65.4%, respectively (p = 0.92, log-rank test). CONCLUSIONS: Adjuvant RT for centrally located HCCs after narrow-margin hepatectomy was technically feasible and relatively safe. No significant between-group difference was observed in recurrence-free and overall survival. The post-hoc subgroup comparison showed that adjuvant RT improved recurrence-free survival considerably, but not overall survival, in patients with small HCCs (<= 5 cm). More in-depth studies are needed to validate this finding. (C) 2014 by the American College of Surgeons