Treatment characteristics and mortality of a large insured female population with advanced or metastatic breast cancer by receipt of HER2-targeted agents

Purpose: This retrospective administrative claims study of women diagnosed with advanced or metastatic breast cancer compared treatment characteristics and mortality by receipt of human epithelial growth factor receptor 2 (HER2)-targeted agents and by disease stage and age group among patients using HER2-targeted agents. Patients and methods: Adult women diagnosed with stage III or IV breast cancer (index date) between 2008 and 2012 were identified from MarketScan® databases containing medical and pharmacy claims for >40 million enrollees insured with >100 US health plans. Patients were followed until the earlier of the following: end of enrollment, inpatient death, or December 31, 2012. Study cohorts were women ± HER2-targeted agent use, HER2-targeted agent users' subgroups of stages III and IV, and age group. Pre- and postindex breast cancer treatments were compared among study cohorts. Overall survival was compared using log-rank tests. Cox proportional-hazards models were used to study the predictors of overall survival. Results: Of 30,660 eligible women, 14.4% received HER2-targeted agents. HER2-targeted agent users received more aggressive pre- and postindex cancer treatments compared to those with no HER2-targeted agents. HER2-targeted agents had higher rates of pre- and postindex breast cancer surgery, adjuvant/neoadjuvant chemotherapy, radiation therapy, chemotherapy, and biologics-based therapy. Among HER2-targeted agent users, younger women and those with stage III breast cancer received more aggressive treatments. After adjusting for clinically relevant patient characteristics, women receiving HER2-targeted agents had a 20% reduced risk of death compared to patients not receiving HER2-targeted agents. Among all patients and the subset of HER2-targeted agent users, stage IV patients and those in the oldest age group had a higher risk of death. Conclusion: Among patients with advanced or metastatic breast cancer, receipt of HER2-targeted agents was associated with more aggressive treatment and longer survival. Patients with higher stage breast cancer and older patients received less aggressive therapies and had a higher risk of death. Keywords: metastatic breast cancer, HER2, treatment, survival, human epidermal growth factor receptor 2, therapy