Risk factors and survival outcomes in patients with breast cancer and lung metastasis: a population-based study

The risk factors for morbidity and mortality in breast cancer lung metastases (BCLM) patients still remain poorly identified. The aim of this study was to assess the incidence and survival of BCLM and associated risk factors. Patients with BCLM were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Multivariate logistic regression analysis was used to determine the risk factors for BCLM. Predictors of factors associated with death were analyzed in Cox regression and Fine and Gray's test. Of the 11568 patients with stage IV breast cancer, 4213 (36.4%) had BCLM and 1214 (10.5%) had metastases confined to lungs. The median survival time for patients with BCLM was 21 months, and 15.5% of the patients were alive more than 3 years. The tumor subtype distribution was 45.3% HR^- /HER2^- , 12.2% HR⁺ /HER2⁺ , 7.8% HR^- /HER2^+, and 15.0% triple-negative subtype. Compared with patients without BCLM, those with BCLM were more likely to be aged, female, black, higher tumor grade, HR^- /HER2⁺ , HR⁺ /HER2^+, and triple-negative subtypes at diagnosis. Survival analysis showed that the aged, black race, HR^- /HER2⁺ , triple-negative subtype, higher grade were the independent risk factor for BCLM patients' survival, while HR⁺ /HER2⁺ subtype, insured status, and married status suggested better prognosis. In conclusion, the incidence and prognosis of BCLM varied by tumor subtypes, age, and race. Elderly patients with HER2-positive or triple-negative tumors were more likely to have BCLM.