Comparative effectiveness of everolimus-based therapy versus endocrine monotherapy among postmenopausal women with HR+/HER2− metastatic breast cancer: a retrospective chart review in community oncology practices in the US

Everolimus-based therapy and endocrine monotherapy are used among postmenopausal women with hormone receptor-positive human epidermal growth factor receptor-2 negative (HR+/HER2−) metastatic breast cancer (mBC) whose disease progressed or recurred on a non-steroidal aromatase inhibitor (NSAI). However, limited evidence exists regarding the real-world comparative effectiveness of these agents.

This retrospective chart review examined postmenopausal HR+/HER2− mBC patients in community-based oncology practices who received everolimus-based therapy or endocrine monotherapy (index therapy) as any line of therapy for mBC between 1 July 2012 and 15 April 2013 after NSAI failure. Time on treatment (TOT), progression-free survival (PFS), and time to chemotherapy (TTC) from index therapy initiation were compared using Kaplan–Meier analyses and Cox proportional hazards models adjusting for baseline characteristics.

A total of 243 and 270 patients received everolimus-based therapy or endocrine monotherapy in a quota-based sample. Patients treated with everolimus-based therapy had a higher proportion of visceral metastases, high tumor burden, and use of prior chemotherapies for mBC. After adjusting for baseline characteristics, everolimus-based therapy was associated with significantly longer TOT (HR = 0.67, 95% CI: 0.51–0.87) and PFS (HR = 0.75, 95% CI: 0.57–0.98) than endocrine monotherapy. No significant difference was found between everolimus-based therapy and endocrine monotherapy in TTC (HR = 0.81, 95% CI: 0.52–1.27). Results stratified by line of therapy were generally consistent with the overall results.

Limitations include recall and information bias with potentially absent or erroneous chart data, unobserved factors due to non-randomization, inability to measure outcome assessments paired with measuring outcomes prior to exposures, and potential patient selection bias associated with chart review.

Among a nationwide sample of postmenopausal HR+/HER2− mBC patients treated in community oncology settings, treatment with everolimus-based therapy was associated with significantly longer TOT and PFS compared to endocrine monotherapy.