Thermal ablation with and without adjuvant systemic therapy: a nationwide multicenter observational cohort study of solitary colorectal liver metastases

Thermal ablation is routinely used for solitary colorectal liver metastases (SCLM), but the added value of adjuvant systemic therapy in SCLM remains unclear. This study aimed to compare the long-term outcomes for SCLM treated by ablation alone (AB) versus ablation plus systemic therapy (AS).This multicenter retrospective study using nationwide data from fourteen institutions between October 2010 and May 2023, 369 patients with initial SCLM smaller than 5 cm, no extrahepatic metastases, and colorectal cancer R0 resection treated by thermal ablation were included. The crude analysis was used to analyze eligible cases between the two groups. The propensity score matching (PSM) to control for potential confounders in each matched group. Subgroup analyses were performed to identify specific survival benefits.61.2% (226/369) of eligible patients were treated with AS and 38.8% (143/369) with AB. During the median follow-up period of 8.8 years, 1-/3-/5-year DFS/OS rates did not differ between the two groups, when analyzed via PSM (P=0.52/0.08). Subgroup analysis revealed that AS was significantly associated with better OS than AB in patients with plasma CEA >5 ug/L (P=0.036), T (III-IV) category of primary cancer (P=0.034), or clinical risk score (1-2) (P=0.041). In each matched group, we did find a significant difference in drug-related adverse events (P<0.001) between AS group (24.1%, 28/116) and AB group (0.0%, 0/116).For patients with plasma CEA >5 ug/L, T (III-IV) category of primary cancer, or clinical risk score (1-2), thermal ablation plus systemic therapy appeared to be associated with improved overall survival. Thermal ablation was equally effective in disease-free survival for treating solitary colorectal liver metastasis, whether with or without adjuvant systemic therapy.