Estimated Life-Years Saved in Women with HER2-Positive Metastatic Breast Cancer Receiving First-Line Trastuzumab and Pertuzumab in the United States

Background: HER2 positive (HER2+) metastatic breast cancer (MBC) is associated with high mortality. Trastuzumab was approved for use in 1998, but the life-years saved from first-line use are unknown, as are the potential US population benefits from adding pertuzumab. Objectives: The first aim was to estimate the number of life-years saved by using first-line trastuzumab between 1999 and 2013 in HER2 women with MBC. In addition, based on these estimates, the second aim was to project the life-years that could be saved by adding pertuzumab to trastuzumab in first-line therapy. Methods: We constructed a simulation model accounting for incidence, testing rates, therapy utilization, and overall survival. The model was run for 1999 to 2013 (15 years) to estimate the life-years saved from using trastuzumab plus chemotherapy instead of chemotherapy alone. The model was also run from 2013 to 2027 (15 years) to project the life-years that might be saved by adding pertuzumab. Uncertainty was incorporated using Monte Carlo methods. Results: The estimated number of women with HER2 MBC varied over time, with the peak of 9700 in 2005 and the low of 7700 in 2018. The cumulative incremental life-years saved because of first-line trastuzumab use from 1999 to 2013 was estimated to be 156,413 (95% simulation interval 114,840-195,201). The projection for pertuzumab from 2013 to 2027 was 137,959 (95% simulation interval 56,011-225,069). Exploratory analyses of value showed that pertuzumab, trastuzumab, and chemotherapy is associated with a $1.10 billion gain compared with chemotherapy alone, and adding pertuzumab is associated with a $0.06 billion gain compared with trastuzumab with chemotherapy. Conclusions: This simulation model suggests that substantial progress has been made in treating HER2 women over the past 15 years, and the future may witness similar gains with the introduction of pertuzumab.