Occurrence and characterization of everolimus adverse events during first and subsequent cycles in the treatment of metastatic breast cancer.

PURPOSE: Endocrine therapy remains the standard therapy for patients with metastatic hormone receptor (HR)-positive breast cancer. The novel combination of everolimus and exemestane has been shown to prolong progression-free survival but with increased adverse events compared to exemestane alone. In this study, we aimed to describe the frequency and timing of everolimus dose reductions and/or interruptions due to adverse events.
METHODS: This is a single-center retrospective case series including all patients who received everolimus in combination with exemestane from May 1, 2012, through July 31, 2013. The primary objective was to determine the incidence of first-cycle interruptions or dose reductions with everolimus.
RESULTS: Forty-six patients were included in the analysis. First-cycle dose reductions or interruptions were observed in 21 (45.6 %) patients. The most common adverse events leading to dose reduction or interruption was stomatitis (57.1 %), fatigue (14.3 %), and diarrhea (14.3 %). The median time to dose reduction was 14 days, and the median duration of the interruption was 14 days. The median progression-free survival was 6.2 months, and the median time to treatment failure was 4.4 months.
CONCLUSIONS: In this case series, almost half of the patients treated with everolimus and exemestane required a dose reduction or interruption of everolimus during the first cycle of treatment. This early onset of adverse events requires thorough patient education and close clinical monitoring during the first 28 days of therapy.