Background: For the 6% of breast cancer patients with a diagnosis of stage IV disease, systemic therapy is the cornerstone of treatment, with an unclear role for surgery. Limited evidence exists to delineate treatment methods with regard to hormone receptor and human epidermal growth factor receptor 2 (HER2) status.
Methods: The National Cancer Database was used to identify 12,838 stage IV breast cancer patients with known hormone receptor and HER2 status from 2010 to 2015. Chi square tests examined subgroup differences between the treatment methods received. Using the Kaplan-Meier method, 5-year overall survival (OS) was assessed. Multivariate Cox proportional hazard models examined factors associated with survival.
Results: A survival advantage was noted for patients who received either systemic therapy and surgery (ST + Surg: hazard ratio [HR] 0.723; 95% confidence interval [CI] 0.671-0.779) or systemic therapy, surgery, and radiation (Trimodality: HR 0.640; 95% CI 0.591-0.694) (both p < 0.0001) compared with systemic therapy alone (ST). The HER2+ patients who received Trimodality or ST + Surg had a better 5-year OS rate than those who received ST (Trimodality [48%], ST + Surg [41%], ST [29%]; p < 0.0001). The sequence of chemotherapy in relation to surgery is significant, with the greatest survival advantage noted for recipients of neoadjuvant chemotherapy (NAC) compared with patients who had adjuvant chemotherapy when they had positive hormone receptor and HER2 status (HER2 + NAC: HR 0.477; estrogen receptor-positive [ER+] NAC: HR 0.453; progesterone receptor-positive [PR+] NAC: HR 0.448; all p < 0.0001).
Conclusions: Surgery in addition to ST has a survival benefit for stage IV breast cancer patients with known hormone receptor and HER2 status and should be considered after NAC for patients with ER+, PR+, or HER2+ disease.