Abstract P1-16-02: The impact of locoregional treatment on survival in patients with metastatic breast cancer: A national cancer database analysis

Abstract Purpose and Objectives: Although systemic therapy is the standard treatment for metastatic breast cancer, the value of locoregional treatment (LRT) to the primary tumor and its impact on survival is controversial. This study evaluates survival outcomes in patients with metastatic breast cancer after receiving LRT (surgery and/or radiation therapy) to the primary tumor. Materials and Methods: The National Cancer Database (NCDB) identified 16,128 qualifying cases of stage IV breast cancer (M1, 2004-2013) who received systemic therapy with or without local therapy. Treatment modality was divided into surgery, radiation therapy (RT), surgery with RT (Sx+RT), and no LRT. Median survival and three-year actuarial survival rates (OS) were analyzed for each treatment group. On multivariate analyses, adjusted hazard ratios (HR) with 95% confidence interval were computed using Cox regression modeling to adjust for patient characteristics, year of diagnosis, clinical T and N staging, and facility type. Additionally, survival outcomes for each treatment group were analyzed by metastasis groups (bone, visceral, multiple). Results: A temporal trend of each treatment modality used in years 2004 – 2013 illustrated that the relative use of LRT decreased from 47.2% to 36.2% (p for trend = 0.041). Overall, the median follow-up was 28.3 months and median survival for all patients was 37.2 months. With 9,761 deaths reported, the estimated 3-year survival rate for all patients was 51.3%. The Sx+RT group (n = 2,166) had the highest 3-year survival rate of 69.4%, followed by the surgery group (n = 4,293) with 57.6%, no LRT group (n = 8,955) with 44.3%, and RT group (n = 714) with 41.5% (p < 0.0001). On multivariate analysis, a decreased hazard of death (adjusted HR, 95% CI) was noted in radiation patients compared to no LRT group but without statistical significance (0.91, 0.81-1.0, p = 0.057). Patients receiving surgery (0.68, 0.65-0.71, p < 0.0001) and Sx+RT group (0.46, 0.43-0.49, p < 0.0001) reported statistically significant improved survival compared to the no LRT group. Additionally, later year of diagnosis, low Charlson-Deyo score, high income, private insurance, white race, age 18 - <50, low T and N stage, ductal histology, positive ER/PR/HER2 status, bone only metastasis, and academic facility type were considered favorable factors for OS. When stratified by metastasis type, patients with bone metastasis had the longest 3-year survival rates (74.4% for Sx+RT, 69.4% for surgery, 53.8% for no LRT, 49.3% for RT, p < 0.0001) whereas patients with multiple metastases had the worst outcomes (56.0% for Sx+RT, 43.5% for surgery, 37.9% for no LRT, 34.4% for RT, p = 0.003). Conclusion: Patients with metastatic breast cancer have a large range of survival rates. Locoregional treatment, especially surgery followed by RT, in addition to systemic therapy was associated with improved survival in metastatic breast cancer patients. When survival rates for each treatment modality was stratified by metastasis location, the most favorable survival was observed for the surgery with follow-up radiation group, which is consistent with the overall analysis. Citation Format: Kim KN, Huang D, Qureshi MM, Ko NY, Hirsch AE. The impact of locoregional treatment on survival in patients with metastatic breast cancer: A national cancer database analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-16-02.