Abstract B016: Predictors of nonadherence to adjuvant hormonal therapy among breast cancer patients
Authors: Truman Samantha C. , Babatunde Oluwole , Alvarado Christian , Heiney Sue P. , Sellner Joshua E. , Reiss Kelly E. , Adams Swann Arp 
Published: August 2020

Purpose: This study aimed to investigate the predictive factors associated with nonadherence to adjuvant hormonal therapy (AHT) by year among patients with receptor-positive breast cancer.

Background: AHT is used to treat and manage hormone receptor-positive breast cancers, which comprise 70% of all breast cancers. Low adherence to these medications has been shown to increase the risk of death by approximately 20%. Despite the known benefits for reducing mortality and reoccurrence, adherence to AHT medications has proven to be a major challenge for patients. Previous studies have linked several demographic and clinical characteristics as predictors of adherence.

Methods: Women diagnosed with receptor-positive breast cancer between the years 2002 to 2010 were identified through the South Carolina Central Cancer Registry, which was linked to administrative databases, the South Carolina Medicaid Program, and a private payor plan. We identified 1,095 patients with breast cancer who met our eligibility criteria and filled at least two AHT medications. The medication possession ratio (MPR), the ratio of number of pills for each AHT and the number of days between each AHT refill, was derived using automated pharmacy records to identify AHT prescriptions and the dates of each refill. The average MPR was calculated for each year over a 3-year period. Regression models and t-tests were used to assess factors associated with nonadherence of AHT for each of the 3 years.

Results: The average adherence rate for AHT was 0.93, 0.90, and 0.90 following year 1, year 2, and year 3, respectively. For each of the 3 years, African Americans had a significantly lower adherence to AHT compared to European Americans. In addition, women under the age of 50 years had a significantly lower MPR for each year compared to women 50 and older (p = &lt;.01). Insurance type also had a significant impact on compliance over the 3-year period (p = &lt;.01). Women were more likely to be adherent to aromatase Inhibitors (AIs) compared to selective estrogen receptor modulators (SERMs) across all 3 years. Interestingly, geographic location (urban versus rural) did not affect adherence until the third year of treatment (0.91 ± 0.17 vs. 0.87 ± 0.20, p = 0.02, respectively). Treatment factors such as radiation and chemotherapy did not appear to impact AHT adherence. However, upon further investigation, following year 1 of treatment, women taking both AHT and chemotherapy simultaneously, as opposed to only taking AHT, had a significantly lower adherence rate (0.86 ± 0.19 vs. 0.92 ± 0.14, p = &lt;.01, respectively).

Conclusion: Demographic characteristics such as age, race, and insurance type appeared to impact AHT adherence across the initial three years of AHT. However, there are other factors that should be considered at different timepoints during treatment, such as geographic location and treatment regimen. This study provides important insight into probable factors and characteristics that can be used to provide targeted interventions for improving AHT adherence.

Citation Format: Samantha C. Truman, Oluwole Babatunde, Christian Alvarado, Sue P. Heiney, Joshua E. Sellner, Kelly E. Reiss, Swann Arp Adams. Predictors of nonadherence to adjuvant hormonal therapy among breast cancer patients [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr B016.