Abstract P4-14-03: What are the real-world treatment patterns and medical costs in patients with metastatic breast cancer treated with ado-trastuzumab emtansine?
Authors: Cloutier M , Guerin A , Heroux J , Emond B , Wu EQ , Masaquel A , Barnett B 
Published: May 2016

Abstract
Background: Ado-trastuzumab emtansine (T-DM1) was approved by the FDA (02/2013) for the treatment of HER2+ metastatic breast cancer (mBC). This study assessed the real-world treatment (tx) patterns and medical costs in patients (pts) receiving T-DM1 or other targeted therapy [TT] or chemotherapy [CHT] for the tx of HER2+ mBC in the US.
Methods: Adult women with mBC initiated on T-DM1 (index date) covered by their health plan ≥365 days before and ≥30 days after the index date were selected in a large US commercial claims database (Q2 2009–Q2 2014). Pts were observed from the index date to the end of health plan enrollment (study period). Patient characteristics at T-DM1 initiation were reported and tx patterns, including T-DM1 tx duration, discontinuation (no T-DM1 claim for ≥60 days) and switch to a new TT or CHT (among pts who discontinued T-DM1), were analyzed using Kaplan Meier (KM) analyses.
In addition, T-DM1 pts were exactly matched to pts treated with another TT or CHT with similar profiles (same line of therapy and metastatic sites) on a 1:1 ratio. Tx change, defined as the initiation of or a switch to a new TT or CHT, and medical costs, measured up to 6 months after index date, were compared between pts receiving T-DM1 vs. other TT or CHT using multivariate Cox and GLM regression models, respectively.
Results: A total of 240 T-DM1 pts were selected. Mean age was 54 years and pts had on average 2.9 distinct metastatic sites. Most prevalent sites were bone/bone marrow (69.6%), liver (47.1%), and lung/pleura (40.4%). Median time from mBC diagnosis to index date was 25.0 months. Pts were observed for a median of 5.6 months after index date. 8.3% of pts were initiated on T-DM1 in 1st line therapy, 30.4% in 2nd line, 15.4% in 3rd line, 17.5% in 4th line, and 28.3% in later lines. 9.2% of pts were initiated on T-DM1 concomitantly with hormonal therapy. Pts received a mean of 6.2 doses (median: 5.0) of T-DM1 over the study period. KM median T-DM1 tx duration estimate was 7.4 months. KM rates of T-DM1 discontinuation and switch at 6 months were 18.6% and 23.1%, respectively.
Among the matched sample (n=228 in each cohort), T-DM1 pts had a lower risk of tx change (hazard ratio (HR) [95% CI]: 0.61 [0.40; 0.94]) compared to pts treated with other TT or CHT. Among T-DM1 pts, those receiving T-DM1 in 1st or 2nd lines of therapy had a lower risk of tx change than those receiving T-DM1 in later lines (HR [95% CI]: 0.34 [0.14; 0.80]). Once adjusted for potential confounding factors, T-DM1 pts had lower medical costs (adjusted, $1,630 per pt per month [pppm]) compared to pts treated with other TT or CHT (unadjusted, $5,075 vs. $6,204; p&lt;.05). The medical cost difference was mainly driven by the outpatient cost difference (adjusted, $1,002 pppm; p&lt;.05). Incremental cost associated with adverse events accounted for 25% (adjusted, $255 pppm) of the outpatient cost difference.
Conclusions: In this real-world study of mBC pts treated with T-DM1 shortly after its approval, most pts were initiated on T-DM1 in 2nd and later lines of therapy. When compared to pts with similar profiles initiated on other TT or CHT, T-DM1 pts had a lower risk of tx change and lower medical costs.
Citation Format: Cloutier M, Guerin A, Heroux J, Emond B, Wu EQ, Masaquel A, Barnett B. What are the real-world treatment patterns and medical costs in patients with metastatic breast cancer treated with ado-trastuzumab emtansine?. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-03.