Clinical and economic outcomes by first-line treatment among women with HR+/HER2- metastatic breast cancer in a large US health plan database

Background: Guidelines recommend that women with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (mBC) initiate hormonal therapy before chemotherapy. This study compared outcomes of women with mBC who received chemotherapy first vs hormonal therapy.

Methods: A retrospective cohort study of women with mBC was conducted using a large US commercial health plan database between January 1, 2008-April 30, 2013. Subjects had evidence of a HR+/HER2- tumor sub-type in a cancer registry and use of chemotherapy or hormonal therapy in claims. Subjects were continuously enrolled for ≥6 months after metastasis and assigned to cohorts for receiving chemotherapy only or hormonal therapy only during first-line (CT-1L vs HT-1L). Adjusted incidence rates of clinically significant events were compared using a negative binomial model, and adjusted healthcare costs were compared using a generalized linear model.

Results: Three hundred and twenty-four women with HR+/HER2- mBC met the selection criteria; 179 (55%) received CT-1L and 145 (45%) received HT-1L. Mortality rates did not differ between cohorts (unadjusted incidence rate ratio (IRR) = 1.67, 95% CI = 0.82-3.46; adjusted IRR = 0.64, 95% CI = 0.32-1.27). Adjusted average total all-cause healthcare costs were $11 090 for women with CT-1L and $6743 for women with HT-1L (cost ratio =1.64, 95% CI =1.36-1.99).

Conclusions: Observed use of first-line chemotherapy (>50%) was higher than expected given the HR + molecular profile of the tumors. Chemotherapy use during first-line did not appear to be associated with a survival benefit, but was associated with significantly higher costs compared with the use of hormonal therapy during first-line; however, this comparison is limited by demographic and baseline characteristic differences between the two cohorts. This study contributes to understanding real-world treatment patterns and the associated clinical and economic outcomes of using chemotherapy vs hormonal therapy as a first-line treatment option for the HR+/HER2- mBC population.