Adherence and persistence to adjuvant hormonal therapy in early stage breast cancer patients: A population-based retrospective cohort study in Israel.

Abstract

e12051 Background: Adjuvant hormonal therapy has been consistently proven to improve multiple outcomes in early breast cancer. Nonetheless, data on rates of adherence and persistence with therapy outside West Europe and North America are scarce. We assessed the adherence and persistence with adjuvant hormonal in a retrospective population based cohort of breast cancer survivors in Maccabi Health Services (MHS), Israel. Methods: We identified women who were diagnosed with breast cancer and initiated adjuvant hormonal therapy between January 2000 and November 2008. Subjects were followed retrospectively from first dispensed tamoxifen or aromatase inhibitor (AI) and up to the earliest of the following events: disease recurrence (indicated by surgery, radiotherapy, chemotherapy or other related therapies), leaving MHS, death, or completion of 5 years of treatment. Discontinuation of therapy was defined as a 180-day or longer treatment gap. Adherence with therapy was assessed using proportion of days covered (PDC) during follow-up period. Survival analysis was used to determine the effect of adherence on all-cause mortality. Results: A total of 4178 women with breast cancer were followed for a median 7.8 years. Over 90% of patients received tamoxifen as the initial hormonal agent. Mean PDC was 84% with lower rates associated with younger age, smoking status, comorbidities and year of diagnosis. Residential area did not affect adherence. Differences were not found. Discontinuation of therapy occurred in 23% of study patients. Among persistent patients, 70% were optimally adherent with therapy (PDC>=80%). Association between adherence with therapy and survival is investigated. Conclusions: Adherence to adjuvant hormonal therapy among Israeli breast cancer patients with national health insurance is high in comparison to international reports. Nevertheless, suboptimal adherence was identified among younger (<45y) patients. Because of the efficacy of hormonal therapy in preventing recurrence and death in women with early-stage breast cancer, interventions are necessary to identify and prevent suboptimal adherence among high risk subgroups.