Multi-Institutional Proton Beam Therapy Outcomes for Hepatocellular Carcinoma From the Proton Collaborative Group REG001-09 Registry Study.

Purpose: External beam radiation therapy (EBRT) for hepatocellular carcinoma (HCC) is commonly delivered with x-rays, although proton beam therapy (PBT) offers a unique dosimetric advantage that for some patients may translate into meaningful clinical benefit. Most published outcomes of PBT for HCC come from Asian institutions, whereas there is a scarcity of data from Western countries. Methods and Materials: We identified patients with nonmetastatic HCC patients treated with definitive PBT at 9 institutions in the United States and enrolled on the Proton Collaborative Group REG001-09 prospective registry study (NCT01255748). The primary study objective was to describe treatment efficacy and safety outcomes. Results: 88 patients were treated from 2013 to 2021. Median age was 68 years (range, 40-91) most with Eastern Cooperative Oncology Group performance status 0 to 1 (85.0%). Median tumor size was 4.7 cm (range, 1.2-19 cm). Baseline Child-Pugh (CP) class was A or B in 43 (71.7%) and 15 (25.0%), respectively. The median prescribed biologically effective dose (BED Conclusions: Dose-escalated PBT, delivered predominantly with moderate hypofractionation, achieves excellent FFLF with a favorable safety profile. PBT may offer a particular clinical advantage for large HCC and prospective evaluation for this high-risk patient subset is warranted.