HER2-Positive Metastatic Breast Cancer: A Retrospective Cohort Study of Healthcare Costs in the Targeted-Therapy Age

IntroductionClaims data (IBM MarketScan Commercial and MarketScan Medicare Supplemental databases) from June 30, 2011 to September 30, 2017 were used to evaluate the cost impact of human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) in this retrospective cohort study.MethodsThe primary analysis compared short-term costs for patients diagnosed with HER2+ MBC at least 180 days after the end of first HER2-targeted treatment (MBC+ cohort) versus a propensity score matched cohort of patients with breast cancer who did not develop MBC (MBC- cohort). A pseudo-post period for patients in the HER2+ MBC- cohort was defined by indexing to the HER2+ treatment completion-MBC diagnosis time interval of the matched pair in the HER2+ MBC+ cohort; we then compared average monthly cost differences between these groups for the year preceding and following MBC diagnosis. In secondary analyses, we estimated medium-term aggregate and categorical healthcare costs for patients with HER2+ MBC up to 3 years post-diagnosis.ResultsIn the short-term primary analysis, costs for the HER2+ MBC+ and HER2+ MBC- cohorts were largely comparable in the year preceding MBC diagnosis. Monthly direct costs were significantly higher for the HER2+ MBC+ cohort in the months immediately preceding MBC diagnosis, with differences in the range of $500-5000. Following diagnosis, total monthly costs were $13,000-34,000 higher for patients in the HER2+ MBC+ cohort vs. the HER2+ MBC- cohort. In the medium-term secondary analysis, mean per patient total costs were $218,171 [standard error (SE) $5450] in the first year following MBC diagnosis and $412,903 (SE $13,034) cumulatively over 3 years following diagnosis (among patients with complete follow-up). Primary cost contributors were outpatient visits ($195,162; SE $8043) and HER2-targeted therapy drug costs ($177,489; SE $8120).ConclusionsHER2+ MBC is associated with high short-term and medium-term direct healthcare costs. These could be alleviated with early diagnosis and optimal standard-of-care treatment for early breast cancer, which can significantly reduce the risk of recurrence.