Treatment patterns by lines of therapy in metastatic breast cancer: Evidence from a large insured population in the United States.

Abstract

116 Background: Metastatic breast cancer (mBC) guidelines contain multiple lines of treatment (LOTs) and regimen options, however little data on treatment patterns is available from real world clinical practice. This study describes patterns of chemo and biologic therapy use by LOT observed within a large U.S. insured population. Methods: Adult women with newly diagnosed mBC and starting anti-neoplastic treatment were identified in the 2005-2009 MarketScan Database which contains medical, pharmacy claims of > 40 million enrollees insured with >100 health plans across the United States. The index date was the first prescription fill or administration of anti-neoplastic treatment following metastatic diagnosis. A 90-day gap in treatment or initiation of a new regimen defined the end of a LOT. Patient demographics and clinical characteristics were measured at index. Descriptive analyses included the distribution of patients, use of chemo and biologic therapies and their therapy duration, across the first 4 LOTs observed. Results: Of 7,767 patients identified (mean (SD) age=58.2 (11.9) years), ≥50% received a subsequent LOT across the 4 LOTs (2nd LOT n=4,077, 3rd LOT n=2,033, 4th LOT n=1,059). Bone (44%) was the major metastatic site at diagnosis. The days on therapy (mean, SD, median) varied across LOTs: (162.7, 176.9, 108.0) in 1st, (147.5, 146.7, 99.0) in 2nd, (139.9, 131.1, 99.0) in 3rd, and (130.9, 123.4, 94.0) in 4th LOT. The most common backbone chemotherapies were: paclitaxel (26%), capecitabine (22%), docetaxel (22%) in 1st; paclitaxel (28%), capecitabine (18%), gemcitabine (16%) in 2nd; paclitaxel (22%), gemcitabine (19%), capecitabine (16%) in 3rd, and gemcitabine (19%), paclitaxel (18%), capecitabine (16%) in 4th LOT. Trastuzumab was the most frequently used biologic across all 4 lines (20%, 19%, 19%, 19% in 1st to 4th LOT respectively) followed by bevacizumab (20%, 19%, 19%, 19% in 1st to 4th LOT respectively). Lapatinib was used in 3rd (6%) and 4thLOTs (8%) only. Conclusions: Frequency and duration of chemo and biologic therapy use varied by LOT. The most frequently used agents across the 4 LOTs were paclitaxel (chemo backbones) and trastuzumab (biologics). Number of patients halved with each subsequent LOT.