Compliance with anti-hormonal therapy after omission of radiation following breast-conserving surgery in favorable older patient subgroup

Background/Objective: Anti-hormonal therapy is fundamental in the treatment of hormone-positive breast cancer. Several studies have suggested that omission of radiation in breast-conserving therapy is reasonable in older patient subgroups with favorable tumor characteristics, especially if the patients will receive anti-hormonal therapy. Commitment to anti-hormonal therapy is essential for these patients; however, compliance with the full regimen is not guaranteed. We aim to define anti-hormonal therapy compliance at our institution for this subgroup of older patients, both who underwent radiotherapy and those who opted out of radiotherapy. Methods: Our IRB-approved breast cancer registry database was used to identify women over 65 years old with a T1-T2, ER-positive primary breast cancer who had undergone breast-conserving surgery from 2010 to 2013 (allowing for 5 years of follow-up). Radiotherapy completion rates and duration of compliance to anti-hormonal therapy were defined. Compliance was defined as completing 60 months of anti-hormonal therapy as prescribed by the treating medical oncologist. Results: We identified 188 patients age ≥65 years who underwent breast-conserving surgery with negative margins for a T1-T2, ER-positive primary breast cancer between the years of 2010-2013. Of these, 93.6% underwent radiotherapy, and 6.4% opted out of radiotherapy. Of those that completed radiotherapy, only 56.3% competed 5 years of anti-hormonal therapy, and the remaining 43.8% were considered non-compliant. Of the patient subgroup who chose to omit radiotherapy, only 25% completed anti-hormonal therapy. The remaining 75% were non-compliant. Overall, most patients in this subgroup completed radiotherapy as part of breast-conserving therapy, but only 56% of these completed 5 years of anti-hormonal therapy. Of those that omitted radiotherapy, despite the known importance of antihormonal therapy compliance, only 25% completed the 5 years of anti-hormonal therapy. Conclusions: These findings suggest that anti-hormonal therapy compliance is less than ideal across this population, regardless of the acceptance of radiotherapy (60 months of anti-hormonal therapy was completed by 56% for those who received radiotherapy and 25% for those who did not). This is important to consider when evaluating patients in this age group with favorable tumor biology who may be eligible to omit radiotherapy, as commitment to anti-hormonal therapy compliance is paramount. Further research is necessary to solidify these results and to define outcomes including local-regional recurrence rates, disease-free survival, and overall survival