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.