Stereotactic body radiation therapy for small (<= 5 cm) hepatocellular carcinoma not amenable to curative treatment: Results of a single-arm, phase II clinical trial

Background/Aims: Stereotactic body radiation therapy (SBRT) is used as an alternative ablative treatment in patients with hepatocellular carcinoma (HCC) not suitable for curative treatments. The purpose of this prospective study was to evaluate the long-term efficacy of SBRT for small (<= 5 cm) HCCs. Methods: A phase II, single-arm clinical trial on SBRT for small HCCs was conducted at an academic tertiary care center. The planned SBRT dose was 45 Gy with a fraction size of 15-Gy over 3 consecutive days. The primary endpoint was 2-year local control rate. Radiologic responses were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1) and the modified RECIST criteria. Results: Between 2013 and 2016, 50 patients (53 lesions) were enrolled, with a median follow-up period of 47.8 months (range, 2.9-70.6). Patients' age ranged from 41 to 74 years, and 80% were male. Median tumor size was 1.3 cm (range, 0.7-3.1). The 2- and 5-year local control rates were 100% and 97.1%, respectively. The 5-year overall survival rate was 77.6%. Six months after SBRT, radiologic responses were evident in 44 lesions (83%) according to the RECIST criteria and 49 (92.4%) according to the modified RECIST criteria. None of the patients showed grade >= 3 adverse events. Conclusions: SBRT showed excellent results as an ablative treatment for patients with small HCCs while showing minimal toxicities. SBRT can be a good alternative for both curative and salvage intents in patients with HCCs that are unsuitable for curative treatments.