5-year adherence to adjuvant endocrine treatment in Dutch women with early stage breast cancer: a population-based database study (2006-2016).

Abstract PurposeHormonal receptor (HR) positive breast tumors are common. Adjuvant hormonal therapy (AHT) with Tamoxifen or Aromatase Inhibitors (AIs) is beneficial depending on the stage of the tumor. Despite the fact that AHT has been shown to improve survival and recurrence, Dutch adherence rates, which were mostly dependent on Tamoxifen prescriptions until 2006, plummeted from 80% after one year to 50% after five years. Nonadherence with AHT reduces its effectiveness. This research presents more recent adherence statistics (from 2006 to 2016) as well as factors that influence AHT adherence. In addition to Tamoxifen data, AIs are now included in prescriptions.MethodsThe Netherlands Cancer Registry (NCR) was used to find women with early-stage breast cancer who started AHT within a year of surgery and were linked to the PHARMO Database Network. The Kaplan-Meier approach was used to measure AHT adherence five years after treatment was started, with a 60-day gap between refills as our primary outcome. Furthermore, the Medication Possession Rate (MPR) was determined using a cutoff of 50%. Subgroup analysis was performed on influential factors of adherence.Results The 5-year adherence rate was 46.6% when gaps of 60 days between refills were allowed. Based on MPR 80 %, the five-year adherence rate was 53.3%. Age, ≥ 70 years (HR (95% CI) 1.20 (1.10 – 1.30), 50-69 years (HR (95 % CI) 1.09 (1.02 – 1.17) vs < 49 years), and year of diagnosis, 2011-2016 (HR (95 percent CI) 2.39 (2.24-2.56) vs 2006-2010) were also linked with adherence continuance.ConclusionDutch 5-year AHT adherence has remained poor.