Abstract 308P
Background
The brain is a common site of metastasis among HER2-positive (HER2+) metastatic breast cancer (MBC) patients. However, data on the outcomes of patients with brain metastases (BM) versus other sites in the real-world are limited.
Methods
The full analysis included adult HER2+ MBC patients with and without BM identified in the Flatiron database from January 1, 2013 to May 31, 2019. To account for changes in systemic treatment options, e.g. introduction of trastuzumab emtansine (T-DM1), analysis was conducted in a subgroup of patients diagnosed after January 1, 2016. The study objectives were to explore outcomes and treatment patterns among patients with and without BM using electronic health records. Patient demographics, clinical characteristics, overall survival (OS), and treatment patterns were described. Adjusted cox proportional hazards models were used to compare OS across groups.
Results
The full analysis included 3,367 patients, and the subgroup included 1,755 patients. Patients with BM at MBC diagnosis (baseline BM) were younger than those without baseline BM (56.6 vs. 61.4 years). Among those without baseline BM, average time to BM diagnosis was 17.0 months. In both the full analysis and the subgroup, OS was shortest in patients with baseline BM (median OS 24.0 and 22.3 months, respectively), followed by patients without baseline BM who subsequently developed them (median OS 35.7 and 33.8 months). Patients without BM had the longest OS (median OS 41.1 months [40.2 months in the subgroup]). Patients with BM at any point had significantly shorter OS than patients without (HR 1.54, CI 1.28-1.85). Trastuzumab + pertuzumab-based therapy was the most common regimen in both 1L and 2L for patients with and without BM. Among BM patients, T-DM1 was the most common 3L regimen. Trastuzumab-based regimens were most common in 4L and 5L. Lapatinib regimens were used more frequently among BM patients, but were used in only 11-15%, depending on line of therapy.
Conclusions
BM remain a significant burden among patients with HER2+ MBC and are associated with significantly increased risk of mortality. Treatments that improve outcomes for HER2+ MBC patients who are at risk of developing BM over their disease course are needed.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Seattle Genetics.
Funding
Seattle Genetics.
Disclosure
N. Lindegger: Shareholder/Stockholder/Stock options, Full/Part-time employment: Seattle Genetics; Shareholder/Stockholder/Stock options: Roche. C. Ike: Shareholder/Stockholder/Stock options, Full/Part-time employment: Seattle Genetics. N.R.M. Schwartz: Full/Part-time employment, Paid student consultant: Seattle Genetics. A. Surinach: Research grant/Funding (institution), Paid consultant for this study: Seattle Genetics. Y. Liu: Research grant/Funding (institution), Paid consultant for this study: Seattle Genetics. A. Forero-Torres: Shareholder/Stockholder/Stock options, Full/Part-time employment: Seattle Genetics. K. DeBusk: Shareholder/Stockholder/Stock options, Full/Part-time employment: Seattle Genetics; Shareholder/Stockholder/Stock options: Roche.