Survival benefits associated with being adherent and having longer persistence to adjuvant hormone therapy across up to five years among U.S. Medicare population with breast cancer.

purposeTo assess associations between adherence to and persistence with adjuvant hormone therapy and mortality among older women with breast cancer.

methodsThe surveillance, epidemiology, and end results data linked with U.S. Medicare claims was used. This study included older women diagnosed with stage I-III hormone receptor-positive breast cancer from 2009 through 2017. Adherence was defined as having proportion of days covered (PDC) ≥ 0.80. Persistence was defined as having no discontinuation, i.e., no break of ≥ 180 continuous days. Length of persistence was calculated as time from therapy initiation to discontinuation. Cox models with time-dependent covariates were used to assess associations between adherence and persistence with mortality.

resultsThis study included 25,796 women. Adherence rates were 78.1 percent, 75.2 percent, 72.4 percent, 70.0 percent, and 61.5 percent from year 1 to year 5 after hormone therapy initiation. Persistence rates were 87.5 percent, 81.7 percent, 77.1 percent, 72.9 percent, and 68.9 percent through cumulative intervals of 1 year up to 5 years. Adherence was associated with all-cause mortality but not associated with breast cancer-specific mortality. Persistent women had lower risk of all-cause mortality and breast cancer-specific mortality. Each additional year of persistence had additional contributions to survival benefits (11% decreased risk of all-cause mortality and 37% decreased risk of breast cancer-specific mortality).

conclusionThis study confirms the detrimental effect of nonadherence to adjuvant hormone therapy across up to 5 years on all-cause survival in older U.S. women. It also reveals the survival benefits associated with having longer persistence across up to 5 years.