Surgical resection versus stereotactic body radiotherapy for oligometastatic breast cancer to the liver.

Comparative evidence for hepatic resection and stereotactic body radiotherapy (SBRT) in breast cancer liver oligometastases remains limited. We compared survival, progression, and recovery after these treatments. This three-center retrospective study included adults with breast cancer and ≤ 3 liver metastases undergoing hepatic resection or SBRT between 2010 and 2023. Patients with uncontrolled extrahepatic disease were excluded. Propensity score matching generated 1:1 treatment pairs. Overall survival (OS) was the primary endpoint. Adjusted Cox models evaluated OS and progression-free survival (PFS); progression outcomes were analyzed with death as a competing event. Among 1,055 eligible patients, 708 were matched (354 per group). During a median follow-up of 54.8 months, 432 deaths occurred. Median OS was 48.3 months after surgery and 38.8 months after SBRT (adjusted hazard ratio [HR] for SBRT versus surgery, 1.24; 95% confidence interval [CI], 1.02-1.50). Median PFS was 21.8 and 19.7 months, respectively (adjusted HR, 1.13; 95% CI, 0.96-1.33). The 24 month cumulative incidence of treated-site local failure was 7.1% versus 6.5% (adjusted subdistribution HR, 1.12; 95% CI, 0.75-1.68). Median hospital stay was 8 versus 1 day; among patients restarting systemic therapy, median restart intervals were 45 versus 18 days. The OS association became less precise in analyses restricted to R0 resection or liver-only disease. Resection was associated with longer OS, while SBRT was associated with shorter hospitalization and treatment interruption. Uncertain differences in PFS and local failure do not establish equivalence. Residual confounding and treatment heterogeneity limit causal interpretation and warrant prospective comparative evaluation.