What question did this study set out to answer?

To assess the impact of adjuvant endocrine therapy on recurrence and mortality risks in older women with HR+ early-stage breast cancer.

February 19, 2026

Abstract PS2-02-10: The Benefit and Burden of Adjuvant Endocrine Therapy for Older Individuals with Early Stage, Hormone Receptor Positive Breast Cancer

Puntos clave

To assess the impact of adjuvant endocrine therapy on recurrence and mortality risks in older women with HR+ early-stage breast cancer.
Population-based cohort study of individuals >65 years with T1N0 HR+ EBC
Follow-up included 3486 individuals treated with breast-conserving surgery and RT
Adherence to ET assessed at >65% usage over a 2-year interval
Cumulative incidence calculated for local recurrence, contralateral breast cancer, and mortality
Difference-in-differences analysis with Poisson regression for health service utilization
>65% adherence to ET yielded a modest reduction in 10-year local recurrence risk among those receiving RT (0.2% vs 3.4%)
Greater reduction in local recurrence risk for non-RT patients (>65% ET: 1.8% vs no ET: 7.0%)
>65% adherence to ET linked to a small reduction in breast cancer mortality (0% vs 3.3%)
Increased health service utilization due to ET, especially for individuals >65% adherent

Resumen

Abstract Purpose To determine the impact of adjuvant endocrine therapy (ET) among older women diagnosed with hormone positive (HR+), early-stage breast cancer (EBC) on the risks of recurrence and death, and on services utilization. Methods: We identified a population-based cohort of individuals 65 years with T1N0 HR+EBC, treated with breast-conserving surgery (BCS), with or without breast radiotherapy (RT), from Jan 2012- Aug 2021, and followed until December 2023. Exposure to ET was calculated for the 2-year interval following diagnosis, with ET adherence defined as ET use for 65% of the interval, with 1:1 matching performed for cases 65% adherent and those without ET exposure. We calculated the cumulative incidence of ipsilateral local recurrence (LR), contralateral breast cancer (CBC), and breast cancer mortality, adjusting for competing risk of death and stratified by receipt of RT. A difference-in-differences analysis with a Poisson regression was used to compare health service utilization between cases and controls. Results The study cohort included 3486 individuals (median age 71 years, 2,796 received RT); with 1162 in each group (65% adherent, 65% adherent, and no ET). Among individuals who received RT, 65% adherence to ET was associated with a small absolute reduction in the 10-year cumulative risk of LR compared to no ET (65% ET: 0.2% (95%CI: 0.05, 0.84); no ET: 3.4% (95%CI: 1.75, 5.93; p=.01)). There was no difference in 10-year risks of CBC or breast cancer mortality. Among individuals who did not receive RT, 65% adherence to ET was associated with a greater reduction in 10-year LR risk (1.8% (95% CI: 0.33, 6.13) vs 7.0% (95%CI: 3.6, 12.0; p=.04)) and a small reduction in breast cancer mortality (0% vs 3.3% (95% CI: 1.2, 7.3; p=0.03)), compared to those who did not receive ET. Health care utilization was significantly increased with ET use and was greatest for individuals 65% adherent, with significantly more diagnostic imaging tests, primary care, and specialist physician visits compared to those who did not receive ET (Table). Individuals 65% adherent had a smaller absolute benefit from ET, but similarly high health service utilization. Conclusions For older individuals with stage T1N0 HR+EBC, adjuvant ET is associated with a significant increase in health care utilization. For individuals treated with BCS+RT, ET was associated with a small absolute reduction in LR but no difference in CBC or BC mortality, suggesting that the burden of ET may outweigh the benefit in this population. Citation Format: D. Rodin, R. Sutradhar, E. Hahn, K. Jerzak, L. Nguyen, S. Trebinjac, L. Laszat, E. Rakovitch. The Benefit and Burden of Adjuvant Endocrine Therapy for Older Individuals with Early Stage, Hormone Receptor Positive Breast Cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-02-10.

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