Time on treatment of everolimus and chemotherapy among postmenopausal women with hormone-receptor-positive/human-epidermal-growth-factor-receptor-2-negative metastatic breast cancer: a retrospective claims study in the US

Objective: This study aimed to compare time on treatment (TOT) among patients treated with everolimus and chemotherapy, two commonly used treatments for hormone-receptor-positive/human-epidermal-growth-factor-receptor-2-negative (HR+/HER2-) metastatic breast cancer (mBC). Methods: Postmenopausal women with HR+/HER2- mBC who initiated >= 1 new line of therapy for mBC during 20 July 2012-31 March 2014 after a non-steroidal aromatase inhibitor were identified from MarketScan and PharMetrics databases (2002Q1-2014Q2) using a claims-based algorithm. Patients were classified into treatment groups by regimen and line of therapy, and were followed until discontinuation of therapy, end of insurance eligibility, or data cut-off (30 June 2014). Discontinuation was defined as a treatment gap of >= 60 days; patients who did not discontinue were censored at the end of follow-up. TOT was compared between everolimus, chemotherapy, and capecitabine monotherapy using Kaplan-Meier analyses and multivariable Cox models adjusting for line of therapy, age, insurance, de novo mBC diagnosis, prior use of chemotherapy for mBC, sites of metastases, and Charlson comorbidity index. Results: Across the first four lines of therapies for mBC, a total of 940 everolimus, 3410 chemotherapy, and 721 capecitabine monotherapy regimens were included. Based on the different lines of therapies, the median TOT ranged from 5.5 to 7.2 months for everolimus, 4.3 to 4.7 months for chemotherapy, and 3.5 to 6.0 months for capecitabine monotherapy. Pooling all lines of therapies, everolimus was associated with significantly longer TOT compared to chemotherapy (multivariable-adjusted hazard ratio [HR] = 0.69, 95% confidence interval [CI]: 0.62-0.76) or capecitabine monotherapy (multivariable-adjusted HR = 0.73, 95% CI: 0.64-0.83). Longer TOT was consistently observed for everolimus for each line of therapy. Limitations: Proxies used for identifying HR+/HER2- mBC and treatment line, lack of certain clinical factors in claims data, generalizability limited to commercially insured patients in the US. Conclusions: This study found that HR+/HER2- mBC patients receiving everolimus experienced significantly longer TOT than those receiving chemotherapy overall or capecitabine monotherapy.