Of the approximately 67,000 women diagnosed with metastatic breast cancer (mBC) annually in the U.S., nearly 10,700 are HER2-positive (HER2+). Prior to the advent of HER2 targeted therapy, women with HER2+ mBC had a less favorable prognosis than those with HER2-negative mBC. The objective of this study was to quantify survival gains for women with HER2+ mBC from 1995-2015, a period spanning pre HER2 targeted therapy to the present, where multiple targeted therapies are available.
We developed a simulation model to estimate overall survival (OS) for successive cohorts diagnosed with HER2+ mBC from 1995-2015. OS data were derived from clinical trials referenced in NCCN guidelines and extrapolated to a lifetime horizon by fitting Weibull curves. Patients were assigned to regimens in each diagnosis year using information from the IPSOS ‘Global Oncology Monitor’- a commercial treatment registry. Results were calibrated with SEER OS data. Outcomes included 5-year OS, expected OS, and total life years (LYs) for all patients with HER2+ mBC. Annual incidence of HER2+ mBC was assumed to be constant over time.
Over the period 1995-2015, expected 5-year OS for women with HER2+ mBC increased by 28.9%. Mean expected per-patient OS improved by 28.1 months (25,000 population LYs) (see Table). The largest gain (15.7 months) occurred between 2010 and 2015–the period over which pertuzumab-based treatment was approved for first-line use and gained substantial market penetration. The smallest gain (2.4 months) occurred between 1995 and 2000—the period over which trastuzumab-based treatment was approved, but had not yet achieved market penetration.
The introduction and expanded use of targeted treatments, along with other advances in care, have provided substantial individual- and population-level survival gains for women with HER2+ mBC. A considerable proportion of the expected OS differences between 1995 and 2015 took place after the introduction and uptake of trastuzumab and pertuzumab-based regimens.Table:
|Diagnosis Year||5-Year OS (%)||Mean Per-Patient OS (Months)||Population Life Years|
Clinical trial identification
Legal entity responsible for the study
J. Roth, S. Sullivan, S. Ramsey: Research funding from Genentech, Inc. P. Bajaj, C. Reyes, V. Antao, A. Stein: Employee of Genentech, Inc; Stock Ownership in Roche. R. Mahtani: Advisory boards for Genentech, Pfizer, Amgen, Celgene, Sandoz; Research support from Genentech.