Prescription Patterns, Initiation, and 5-Year Adherence to Adjuvant Hormonal Therapy among Commercially Insured Patients with Breast Cancer

BACKGROUND:Tamoxifen and aromatase inhibitors (AIs) are used as adjuvant hormonal therapy (AHT) for early-stage hormone receptor-positive (HR+) breast cancer. Treatment for 5 years reduces cancer mortality by 30%. Despite this benefit, adherence to AHT has been suboptimal. Here, we evaluated AHT initiation and patient adherence in women with private health insurance.MATERIALS AND METHODS:Female patients with breast cancer ≥ 18 years of age who underwent mastectomy or lumpectomy between 1999 and 2015 were identified in the IBM MarketScan Research Database. AHT initiation and adherence rates were estimated for all AHT users regardless of HR+ status. Initiation rates were standardized using HR+ breast cancer incidence rates in the Surveillance, Epidemiology, and End Results (SEER) program. Adherence was defined as medication possession ratio ≥ 80%. Risk ratios, odds ratios, and their 95% CIs were calculated for factors associated with patients' initiation and adherence.RESULTS:Among 80,224 patients, the raw initiation rate was 71.8% and the standardized rate was 87.5%. We found 61.2% patients initiated treatment with AIs and 38.8% with tamoxifen. Patients' 1-year adherence rate was 84.4% and the 5-year rate was 65.2%. Prescription by mail-in order, using a single AHT regimen, 50 to 69 years of age, monthly out-of-pocket drug payment ≤ $11, in US dollars, no depression, no comorbidity, living in the Northeast, treatment in recent years, and receipt of a combination of chemotherapy, radiation, and surgery were associated with better adherence.CONCLUSION:Five-year AHT adherence rates are low among female patients with breast cancer with private health insurance. Effective approaches to improve AHT adherence are needed.