Adoption and effectiveness of de-escalated radiation and endocrine therapy strategies for older women with low-risk breast cancer.

Purpose: Recent clinical trials support de-escalation of adjuvant radiation therapy following lumpectomy in some older women with low-risk HR+ breast cancers planning to take endocrine therapy. The adoption of these findings into clinical practice, and the effectiveness of de-escalated therapy in real-world populations, remain under investigation.
Materials and Methods: We evaluated use of adjuvant radiation therapy and/or endocrine therapy among older women with T1-2 node-negative, HR+ breast cancer in the United States between 2007 and 2011. The study included patients from the Surveillance, Epidemiology and End Results-Medicare linked database and the North Carolina Cancer Information and Population Health Resource database.
Results: Radiation therapy was received by 65.5% of patients, with no decrease over time. Older women and those with T2 (compared to T1) tumors were less likely to receive radiation therapy. In propensity-adjusted analyses, both radiation therapy alone (HR 0.75, 95% CI 0.67-0.84) and radiation + endocrine therapy (HR 0.62, 95% CI 0.54-0.69) were associated with significantly lower recurrence risk compared to endocrine therapy alone. Non-adherence to endocrine therapy was common (37%) and similar across groups. With a median follow-up of 48 months (range 13-84), we were not able to detect an association of non-adherence with recurrence risk in endocrine therapy-containing treatment arms.
Conclusion: Most older women with stage I HR+ breast cancers continue to receive radiation, at higher rates than patients with node-negative stage II tumors. These findings suggest that while multiple evidence-based treatment options exist in these patients, improvements are needed to ensure that radiation therapy is applied equitably and rationally.
Competing Interests: Declaration of Competing Interest Dr. Meyer is currently employed by Roche, Inc. in a non-development role; Dr. Meng is founder and owner of the contract research company Element Stat Inc.; Jason Rotter is currently employed by Mathematica, Inc. Their work on this manuscript was done as employees of UNC Chapel Hill. The other authors have no current or past conflicts of interest to report.
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