Locally Ablative Therapies in Oligometastatic Breast Cancer

Importance: Management of de novo metastatic breast cancer (dnMBC) often focuses on palliation. As such, the potential survival benefit of surgery or ablative therapy remains unclear, particularly for those with oligometastatic disease. Objective: To evaluate the association of surgical and/or locally ablative treatment of the primary and/or metastatic sites with overall survival (OS) in patients with single-site oligometastatic dnMBC. Design, Setting, and Participants: This was a retrospective cohort study using the National Cancer Database. Patients diagnosed with oligometastatic, single-site (ie, brain, bone, liver, or lung) dnMBC receiving systemic therapy were selected from the National Cancer Database (2010-2020). Study groups included no locally ablative therapy/surgery (NLT), primary breast tumor resection only (BR), metastatic site ablative therapy only (MT), and both therapies (BR+MT). Logistic regression identified factors associated with treatment strategy. Multivariable modeling was used to estimate the association of treatment with OS. Data were analyzed from August 2024 to September 2025. Exposures: NLT, BR, MT, or BR+MT therapies for oligometastatic, single-site dnMBC. Main Outcomes and Measures: The primary outcome measure was OS. Results: Among 22 433 patients (median [IQR] age, 61 [50-70] years; 22 126 female biological sex at birth [98.6%]; median [IQR] follow-up, 61.5 [60.7-62.5] months), bone-only metastases were most common in 15 441 (68.8%). Locally ablative therapies were uncommon (BR+MT, 1438 [6.4%]; MT, 2381 [10.6%]; BR, 3435 [15.3%] vs NLT, 15 179 [67.7%]). Older age (>70 years, odds ratio [OR], 2.49; 95% CI, 2.24-2.76 vs <50 years [reference]) and higher comorbidity score (>2, OR, 1.36; 95% CI, 1.16-1.60 vs 0 [reference]) were associated with NLT. Compared with NLT, BR (hazard ratio [HR], 0.62; 95% CI, 0.58-0.67) and BR+MT (HR, 0.60; 95% CI, 0.54-0.67) were associated with improved survival, but OS was worse for MT (HR, 1.22; 95% CI, 1.14-1.31). Conclusions and Relevance: Results of this cohort study suggest that few patients with single-site dnMBC undergo surgical/ablative therapy, although BR+MT and BR only were associated with improved OS. However, if invasive interventions are considered for patients with single-site dnMBC, resection of the breast primary may be beneficial.