The Impact of Primary Tumor Surgery on Survival in HER2 Positive Stage IV Breast Cancer Patients in the Current Era of Targeted Therapy.

OBJECTIVE: We sought to examine the impact of primary tumor resection on survival in HER2+ stage IV breast cancer patients in the era of HER2 targeted therapy. METHODS: We conducted a retrospective cohort study of women with HER2+ stage IV breast cancer in the National Cancer Database from 2010 to 2012 comparing those who did and did not undergo definitive breast surgery. RESULTS: Of 3231 patients, treatment included primary site surgery in 35.0%; chemo/targeted therapy in 89.4%; endocrine therapy in 37.7%; and radiation in 31.8%. Surgery was associated with Medicare/other government (OR 1.36, 95% CI 1.03-1.81) or private insurance (OR 1.93, 95% CI 1.53-2.42) versus none/Medicaid, radiation (OR 2.10, 95% CI 1.76-2.51), chemo/targeted therapy (OR 1.99, 95% CI 1.47-2.70), and endocrine therapy (OR 1.73, 95% CI 1.40-2.14). Non-Hispanic Black versus White patients (OR 0.68, 95% CI 0.53-0.87) were less likely to have surgery. Overall mortality was associated with insurance (Medicare/other government versus none/Medicaid, HR 0.36, p < 0.0001), receipt of chemo/targeted therapy (HR 0.76, p = 0.008), endocrine therapy (HR 0.70, p = 0.0006), and radiation therapy (HR 1.33, p = 0.0009), NH Black versus White race/ethnicity (HR 1.39, p = 0.002), visceral versus bone-only metastases (HR 1.44, p = 0.0003), and lowest versus highest income quartile (HR 1.36, p = 0.01). Propensity score analysis showed surgery was associated with improved survival versus no surgery (HR 0.56, 95% CI 0.40-0.77). CONCLUSIONS: Surgery of the primary site for metastatic HER2+ breast cancer is associated with improved overall survival in selected patients.