Liver metastasis ablation combined with PD-1 inhibitors improves immunotherapy efficacy: A multicenter cohort study

Patients with liver metastases generally have poorer outcomes following immunotherapy compared with those without liver involvement, and whether local ablation can enhance systemic antitumor immunity remains unclear. In this retrospective study, we evaluated the efficacy of combining ablation with PD-1 inhibitor therapy versus PD-1 inhibitor monotherapy in patients with liver metastases. A total of 1337 patients who received PD-1 inhibitors with or without ablation between January 2017 and September 2022 at three institutions were reviewed. After propensity score matching, 234 patients were included, with 117 in the combination group and 117 in the monotherapy group. The combination group achieved significantly longer median overall survival (20.13 vs. 13.83 months, p = .023) and progression-free survival (12.73 vs. 5.20 months, p < .001). Progression of extrahepatic lesions was markedly lower in the combination group than in the monotherapy group (35.9% vs. 66.7%, p < .001). Treatment-related adverse events were common in both groups, with a higher frequency of grade 1-2 events such as transaminase elevation, fever, nausea, vomiting, and abdominal pain in the combination group, while the incidence of grade 3-4 toxicities was comparable between groups and no treatment-related deaths occurred. Multivariate Cox regression confirmed treatment modality as an independent prognostic factor for survival (p < .001). These findings suggest that ablation of intrahepatic lesions may alleviate systemic immunosuppression and augment the efficacy of immunotherapy. The combination of ablation and PD-1 inhibitors represents a promising therapeutic approach for patients with liver metastases.