Evaluation of efficacy and safety of external beam radiotherapy in patients with colorectal cancer liver metastases

OBJECTIVE: This study aimed to evaluate the therapeutic efficacy of external beam radiotherapy (EBRT) in patients with colorectal cancer liver metastases (CRLM) who were either ineligible for or declined surgical resection. Each patient received either intensity-modulated radiation therapy (IMRT) or stereotactic body radiation therapy (SBRT), determined according to tumor size and anatomical location. MATERIALS AND METHODS: Between July 2014 and March 2024, 169 patients with CRLM undergoing medical therapy were enrolled. Propensity score matching (PSM) was used to balance baseline characteristics, resulting in 61 matched pairs (n = 122) for survival and toxicity analyses. Among all patients, 65 received EBRT—36 with SBRT and 29 with IMRT targeting liver metastases, and were included in the local control analysis. RESULTS: After PSM (n = 61 per group), patients treated with “EBRT + medical” therapy exhibited significantly higher survival than those only receiving medical therapy. The median OS was longer in the EBRT group (37.0 vs. 20.8 months, P < 0.001), and PFS was superior too (14.8 vs. 8.17 months, P = 0.001). Local control rates were 82.9% and 67.9% for SBRT at 1 and 2 years, respectively, and 75.5% and 50.6% for IMRT, respectively. EBRT was well tolerated; no radiation-induced liver disease occurred, and no significant differences in adverse event incidence were observed between the medication-only and combined-EBRT groups. CONCLUSION: EBRT represents a safe and effective local treatment option for patients with unresectable CRLM. This study is the first to systematically evaluate IMRT in this population and the first PSM-based comparison of radiotherapy versus no radiotherapy, providing robust evidence for the independent therapeutic benefit of EBRT, however, the retrospective design and potential residual confounding should be considered when interpreting this finding.