Real-World Use Of First-Line Chemotherapy In Post-Menopausal Patients With Hr-Positive Her2-Negative Metastatic Breast Cancer (Mbc) In A Us Community Oncology Network.

561Background: Endocrine therapy (ET) is recommended as 1st line of therapy (LOT) for patients (pts) with HR+/HER2- mBC. Chemotherapy (CT), however, has also been used, though wide practice variation exists. The purpose of this study was to understand the utilization of 1st line CT and its toxicities for HR+/HER2- mBC in a US community oncology setting. Methods: A retrospective study was conducted using US Oncology’s iKnowMed electronic health record database, supplemented with chart review. Post-menopausal women with a diagnosis of HR+/HER2- mBC between Jan. 2010 and Dec. 2013 who received CT as the 1st therapy within 90 days after diagnosis were included. Pts were followed through Dec. 2014 or their last visit. CT regimens and toxicities were analyzed. Results: Of the 8,953 post-menopausal mBC pts, 39.4% (n = 3,525) received at least one CT agent within 90 days after diagnosis. Among those, 598 pts met all inclusion criteria with a final sample of 150 pts, verified by chart review, for analysis. The maj...