Surgery provides survival benefit over systemic therapy alone for stage IV triple negative breast cancer: A propensity matched analysis of the National Cancer Database.
Authors: Cao Lifen , Bliggenstorfer Jonathan T. , Sugumar Kavin , Towe Christopher W. , Li Pamela , Rock Lisa , Shenk Robert , Martin James Michael , Miller Megan E. 
Published: June 2021

e13054 Background: Conflicting data exist regarding benefit of surgery of the primary site for stage IV breast cancer, in which systemic therapy is standard of care and patient characteristics may bias treatment decisions. Metastatic triple negative breast cancer (TNBC) is an aggressive subtype with limited therapy options and poor prognosis. Our aim was to assess whether surgery for the primary tumor in stage IV TNBC provides a survival advantage over systemic therapy alone. Methods: The National Cancer Database was queried for patients with de-novo stage IV TNBC who received systemic therapy alone or systemic therapy and surgery of the primary breast site 2004-2016. Patients receiving surgery for metastatic tumor sites or with incomplete follow up data were excluded. 1:1 propensity matching was performed for demographics, comorbidities, clinical T and N stage, and metastatic sites to minimize confounding factors. Survival outcomes were analyzed using a stratified log-rank test and Cox proportional hazard regression analysis. Results: Of 2989 patients, 782 (26.21%) underwent surgery plus systemic therapy and 2207 (73.84%) were treated with systemic therapy alone. The majority of all patients were aged 51-70 with low co-morbidity, and treated in metropolitan areas. Patients treated at academic facilities (OR = 0.67, p = 0.025), with multiple metastatic sites (OR = 0.59, p < 0.001), or advanced clinical N stage (OR = 0.55, p < 0.001) were less likely to undergo surgery. Of those who completed surgery, 58% had unilateral mastectomy, and 63% had axillary lymph node dissection. Propensity matching identified 507 ‘paired’ patients with similar characteristics in the surgery and systemic therapy alone groups. After multivariable adjustment, surgery was associated with superior overall survival compared with systemic therapy alone (HR 0.73, P < 0.001). Older age (HR = 1.47, p < 0.001), greater comorbidity (HR = 1.28, p < 0.001) and multiple metastatic sites (HR = 1.53, p < 0.001) significantly decreased overall survival in the matched cohort. Median survival was shortest in the systemic therapy alone group (12.8 months, 95% CI 11.3-14.5) and longest in those undergoing systemic therapy plus simple mastectomy (18 months, 95% CI 14.3-21.2), though approximately 4 months of median survival was added for all patients undergoing any surgery vs. systemic therapy alone (p = 0.0001). Conclusions: In stage IV TNBC, surgical resection of the primary tumor site in addition to systemic therapy may provide a survival benefit in selected patients. Though in this retrospective study the sequence of treatment was unknown, surgery could be considered for low disease burden as in other malignancies with oligometastatic disease. Additional research is needed to determine if these findings persist in prospective studies and for other hormone-receptor subtypes.