This study reported outcomes of 41 patients with colorectal cancer liver metastases (63 lesions) treated with PBT to a total dose of 72.6 GyRBE in 22 fractions. The median follow-up period was 27.6 months. The 3‑year LC, OS, and PFS rates were 54.9%, 61.6%, and 16.7%, respectively. No grade ≥ 3 AEs were observed. None of the patients experienced liver failure during the acute or late phase. The authors concluded that care must be taken with tumors that have reduced planning target volume coverage owing to organs at risk restrictions, especially in tumors near the GI tract.