Impact of Endocrine Therapy Adherence on Outcomes in Elderly Women with Early-Stage Breast Cancer Undergoing Lumpectomy Without Radiotherapy

Radiotherapy omission is considered in women >70 years old with ER+ T1N0 tumour post-BCS if the patient receives endocrine therapy (ET). However, the impact of poor adherence to ET on locoregional recurrence (LRR) remains unexplored. This study identified women >70 years old (n=968) with T1-2N0 ER+ breast cancer undergoing BCS without radiotherapy (2004-2019). ET adherence (calculated as duration of treatment over 5 years follow up) was defined as high (<80%) or low (<80%). Within the study cohort, adherence to ET was high in 70%, low in 17%, and 13% took no ET. On multivariate analysis, tumour size (HR 1.67; p=0.04) and high adherence to ET (HR 0.13; p<0.001) were significantly associated with LRR. The 5 year LRR rates were 3.1% with high adherence, 14.7% with low adherence, and 17.9% with no ET. Therefore, higher rates of LRR rates were observed in 30% of women low adherence or no ET.

Classifications: Adjuvant & Neoadjuvant Treatment

Keywords: Radiotherapy Management of the older patient