Brain metastasis in de novo stage IV breast cancer

Objectives: Information of brain metastasis (BM) in de novo stage IV breast cancer is lacking, which is an un-avoidable problem and dilemma in practice. Understanding the current situation is helpful for the clinical cognition and decision-making. Methods: We retrospectively analyzed the clinical and survival information of de novo stage IV breast cancer with BM between 2015 and 2019 from the Surveillance, Epidemiology, and End Results (SEER) database. Multivar-iable logistic and Cox regression analyses were performed to identify predictors of BM and factors associated with all-cause mortality in de novo stage IV breast cancer, respectively. Overall survival (OS) was calculated using Kaplan-Meier and log-rank tests. Results: Our cohort consisted of 1366 patients with BM in de novo stage IV breast cancer, with an incidence of 8.38% in patients with metastatic disease to any distant site. Incidence was highest among patients with met-astatic disease with HR-HER2+ (12.95%) and HR-HER2-(13.40%) subtypes. The higher the number of extra -cranial metastases, the higher the BM incidence. The median OS was 12.0 (95%CI: 10.426-13.574) months in BM group; it was longest in HR + HER2+ (19.0[95%CI: 11.793-26.207] months), and shortest in HR-HER2-(7.0 [95%CI:5.354-8.646] months). Marital status, subtype, and abundance of metastatic sites influenced morbidity and OS of BM in de novo stage IV breast cancer. Conclusions: Population-based estimates of the incidence and prognosis for patients with BM in de novo stage IV breast cancer were closely associated with subtype and metastatic burden. These findings may be helpful in developing diagnostic strategies, especially for brain screening.