SBRT + PD-1 Monoclonal Antibody in Unresectable Colorectal Liver Metastases

For patients with unresectable colorectal cancer liver metastasis, this study aims to explore whether the combination of stereotactic body radiation therapy (SBRT) and PD-1 monoclonal antibody can improve the objective response rate (ORR), achieve better long-term survival benefits, and enhance quality of life. Additionally, the study will investigate the efficacy and safety of SBRT combined with PD-1 monoclonal antibody for treating liver metastases, with the goal of providing high-level evidence-based medical evidence for the use of local hypofractionated radiotherapy combined with PD-1 monoclonal antibody in the treatment of unresectable colorectal cancer liver metastasis. This is a prospective, open-label, multicenter, single-arm, Phase II study. Patients with colorectal cancer will be eligible for enrollment if the hepatobiliary surgery team within the multidisciplinary team (MDT) deems the liver metastases unresectable, and the radiation oncology team within the MDT considers the liver metastases suitable for stereotactic body radiation therapy (SBRT). Enrolled patients will receive hypofractionated radiotherapy with a dose of 8-12 Gy in 5 fractions. Chemotherapy based on 5-FU combined with immunotherapy will be administered before and after radiotherapy. Eight weeks (±2 weeks) after the completion of radiotherapy, radiological assessment or multi-site liver biopsy will be performed. The MDT will then decide on the subsequent management: maintenance chemotherapy or watch-and-wait (W\&W) for patients achieving complete clinical response (cCR) or pathological complete response (pCR), or maintenance chemotherapy or discontinuation for patients who do not achieve cCR/pCR.