ASPO Abstracts
Endocrine therapy initiation within the first year of diagnosis for invasive, hormone receptor-positive breast cancer from 2001-2016, the Kaiser Permanente Breast Cancer Survivors" Cohort
Category: Survivorship & Health Outcomes/Comparative Effectiveness Research
Conference Year: 2022
Abstract Body:
Purpose: Treatment guidelines recommend endocrine therapy for women with estrogen or progesterone receptor positive (ER+ or PR+) breast cancer to reduce second breast cancer events and mortality; however, some eligible women never start endocrine therapy despite studies showing benefits outweigh risks. This retrospective cohort study examined patterns of endocrine therapy initiation within 12 months of diagnosis over time and by demographic, tumor, and treatment characteristics.Methods: We included 7,777 women from three U.S. integrated healthcare systems diagnosed with incident invasive stage I-III ER+ or PR+ breast cancer between 2001-2016. We extracted endocrine therapy from pharmacy dispensings, defining initiation as any dispensings within 12 months of diagnosis. Demographic, tumor, and treatment characteristics were collected from electronic health records. Using generalized linear models with a log link and Poisson distribution, we estimated relative risks (RR) and 95% confidence intervals (CI) of initiating any endocrine therapy, tamoxifen, and aromatase inhibitors (AI) over time and by age, race, stage, histology, grade, tumor size, hormone receptor status, HER2 status, surgery, radiotherapy, and chemotherapy. Analyses were adjusted for age, stage, grade, hormone receptor status, diagnosis year, other treatment, and study site.Results: Among women aged 20+ (mean 61 years), 3,105 (39.9%) initiated tamoxifen first, 3,224 (41.5%) initiated AIs first, and 1,448 (18.6%) did not initiate endocrine therapy. Tamoxifen initiation declined from 67% in 2001 to 15% in 2016. AI initiation increased from 6% in 2001 to 69% in 2016 in women aged ‚â•55 years. The proportion who did not initiate endocrine therapy decreased from 19% in 2002 to 12% in 2014. Women least likely to initiate endocrine therapy were older (RR=0.81, 95%CI=0.77-0.85 for age 75+ vs 55-64), Black (RR=0.93, 95%CI=0.87-1.00 vs white), and had stage I disease (RR=0.88, 95%CI=0.85-0.91 vs stage III).Conclusions: Despite an increase in AI use over time, at least one in six women with ER+ or PR+ breast cancer did not initiate endocrine therapy within 12 months of diagnosis. It is critical to understand barriers to initiation, ensuring all eligible women have opportunities to discuss risks and benefits.
Keywords: breast cancer, endocrine therapy, initiation