3001 - Exploring a Delayed Opt-in Approach to Adjuvant Radiation Therapy in Older Breast Cancer Patients

Purpose/Objective(s): De-escalation of therapy for older women with early-stage breast cancer has been a topic of great interest for decades. While the focus has mostly been on elimination of radiation therapy in favor of endocrine therapy alone, many patients do not tolerate endocrine therapy and may be better served by radiation instead. To more effectively care for this subgroup of patients, we instituted a change in our clinical practice to offer an additional follow-up visit to patients who decline radiation at their first post-operative visit. This follow-up visit is typically 2 months after the initial post-operative visit and is designed to assess tolerance of endocrine therapy and revisit the discussion of radiation. In this study, we sought to quantify the effect of the additional follow-up visit on the number of patients who ultimately opt-in to radiation.

Materials/Methods: We identified all patients age =70 who were seen in consultation by our breast cancer service between July 2022 and December 2024. We selected July 2022 as this was when we first began to implement this change in practice. We then included patients who met the following criteria: received breast-conserving surgery, pTis or pT1, N0 or Nx, ER+, and negative margins. We excluded patients who received chemotherapy or re-irradiation. From this cohort, we assessed the proportion of patients who declined radiation at their first post-operative visit. We then assessed the number of those patients who were offered an additional follow-up visit, who were actually seen for the follow-up visit, and finally the number of patients who opted into radiation at that later time point.

Results: A total of 183 patients met criteria to be included in the current study. Of these, 114 (62%) opted to pursue radiation at their first post-operative visit. Among the remaining 69 patients who declined radiation at their first post-operative visit, 40 (58%) were offered an additional 2-month follow-up visit and 29 (42%) were actually seen for the follow-up visit. Ultimately, 8 of these 29 patients elected to proceed with radiation, representing 20% of the patients offered an additional follow-up visit and 28% of the patients who were seen for that visit. All 8 of these patients were treated with a 5-fraction regimen.

Conclusion: For many older women with early-stage breast cancer, omitting radiation in favor of endocrine therapy alone is an attractive option. However, there is a meaningful proportion of patients – in our study, nearly 30% - who may ultimately opt-in to radiation therapy when presented with the option at a later time point, typically once side effects of endocrine therapy become apparent. We therefore recommend offering additional clinical follow up for these patients.