Real-world treatment patterns and outcomes in HER2 positive MBC patients with brain metastasis in the U.S. community oncology setting.

Abstract

92 Background: Patients (pts) with HER2 positive (HER2+) metastatic breast cancer (MBC) have different patterns of disease and treatment (tx) from HER2 negative MBC. Brain metastasis (BM) frequently occurs and txs vary. Methods: This retrospective study included adult HER2+ MBC pts from a community oncology network electronic health record (EHR) database and diagnosed between 2009-2011, with follow-up until 11/2014. Pts with other primary tumors were excluded. Two cohorts were defined: pts diagnosed with BM and pts with no evidence of BM (NBM), and were initially matched on age and performance status at MBC diagnosis (dx) and stage. Eligibility and txs were examined in electronic chart review. Overall survival (OS) from MBC dx was estimated using a weighted Kaplan-Meier method. Results: The final sample consisted of 86 BM and 101 NBM pts. All baseline MBC demographics were similar across cohorts. Median age was 54 and 52 years for BM and NBM, respectively. The cohorts (BM:NBM) included 57%:75% Caucasians, 12%:6% Blacks, and 31%:19% other/unknown. There were fewer estrogen receptor positive pts in the BM cohort (58%:74%; p = 0.02). Except for bone (p = 0.01), both cohorts had similar prevalence of metastatic sites: liver 35%:35%; lung 31%:30%; bone 41%:62. Of all the BM pts, 54% had first CNS imaging after symptoms, 37% were first imaged for other known reasons. After BM dx, 20% had surgical resection, 67% whole brain radiation (XRT), 37% stereotactic XRT, and 22% palliative XRT (not mutually exclusive). 25% of pts had both XRT and surgery while 72% had only XRT. Among pts receiving systemic therapy after BM dx, the first regimen contained trastuzumab in 55% of pts and lapatinib in 41% of pts. Among pts changing txs after BM dx, 1/3 switched to a trastuzumab but not lapatinib-based regimen; 1/3 to a lapatinib but not trastuzumab-based regimen; 17% to a lapatinib + trastuzumab-based regimen; and 17% to non-HER2-based therapy. Weighted median OS from MBC dx for BM vs. NBM pts was 30.2 and 46.1 months (p = 0.01). Conclusions: For HER2+ MBC pts, survival was shorter for pts with BM vs. NBM and a high degree of tx variability for BM existed. Understanding how detection and tx impacts outcomes will improve care of BM pts.