Abstract 4873: The impact of primary tumor surgery on survival in HER2 positive stage IV breast cancer patients in the current era of targeted therapy
Authors: Mudgway Ross , Villanueva Carlos Chavez de Paz , Lin Ann C. , Senthil Maheswari , Garberoglio Carlos A. , Lum Sharon S. 
Published: August 2019

Objective: While prior studies evaluating the survival benefit from primary site surgery in stage IV breast cancer patients have provided mixed results, it has been well documented that anti-human epidermal growth factor receptor (HER) therapy for metastatic HER2 positive(+) disease improves outcomes. 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 (when mandatory HER2 reporting began) to 2012. Surgical removal of the primary tumor and Cox proportional overall mortality hazard ratios (HR) were assessed. Propensity score matching to diminish selection bias adjusted for demographic, tumor, and treatment variables.

Results: Of 3,231 patients, 71.3% were non-Hispanic (NH) white; 18.4%, NH black; and 5.8%, Hispanic. Bone only metastasis was seen in 25.0% of cases. Treatment included chemo/immunotherapy in 89.4%; endocrine therapy, in 37.7%; and radiation, in 31.8%. Overall, 1,130 (35.0%) underwent primary site surgery and 2,101 (65.0%) did not have surgery. The mean age of those who had surgery was 56.0+13.6 years compared to 59.1+13.7 years who did not (p &lt; .0001). Median follow-up was 21.2 months (range 0-52). Factors associated with increased odds of having surgery included having Medicare/other government or private insurance vs none/Medicaid (OR 1.36, 95% CI 1.03-1.81 and OR 1.93, 95% CI 1.53-2.42, respectively), radiation (OR 2.10, 95% CI 1.76-2.51), chemo/immunotherapy (OR 1.99, 95% CI 1.47-2.70), and endocrine therapy (OR 1.73, 95% CI 1.40-2.14). NH black vs NH white patients (OR 0.68, 95% CI 0.53-0.87) and those treated at an academic/research vs community program (OR 0.67, 95% CI 0.50-0.89) were less likely to have surgery. Overall mortality HR were significantly associated with insurance (Medicare/other government vs none/Medicaid, HR 0.36, p &lt; .0001), receipt of chemo/immunotherapy (HR 0.76, p = .008), endocrine therapy (HR 0.70, p = .0006), and radiation therapy (HR 1.33, p = .0009), NH black vs white race/ethnicity (HR 1.39, p = .002), visceral vs bone only metastases (HR 1.44, p = .0003), and lowest vs highest income quartile (HR 1.36, p = .01). Comorbidities, clinical tumor size, and clinical nodal status were not associated with survival. Propensity score analysis showed surgery was associated with improved survival vs no surgery (HR 0.56, 95% CI 0.40-0.77).

Conclusions: After controlling for covariates, surgery of the primary site in contemporary metastatic HER2+ breast cancer is associated with improved overall survival. If breast surgery is to be considered by patients and providers when deciding treatment strategy, it will be imperative to address significant disparities among patients who are offered surgical therapy.

Citation Format: Ross Mudgway, Carlos Chavez de Paz Villanueva, Ann C. Lin, Maheswari Senthil, Carlos A. Garberoglio, Sharon S. Lum. The impact of primary tumor surgery on survival in HER2 positive stage IV breast cancer patients in the current era of targeted therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4873.