Selective Omission of Oncotype Dx Genomic Testing in Ultra-Low-Risk Luminal A Breast Cancer.

INTRODUCTION: Older women with early-stage luminal A breast cancer have an excellent prognosis with a 5-year relative survival >99%. Research on curtailing overtreatment has challenged historical standards of care by reducing radiotherapy dose and volume, and selectively omitting sentinel lymph node biopsy. This study assessed the utility of Oncotype Dx genomic testing in ultra-low-risk luminal A breast cancer. PATIENTS AND METHODS: A community hospital cancer registry was queried to identify consecutive breast cancer patients from 2014 to 2022. An ultra-low-risk population was defined as age ≥60 years, hormone-receptor positive, HER2-negative, pathologic stage T1b-T2N0 without lymphovascular invasion, and Ki-67 ≤13.25%. Analyses examined the distribution of Oncotype Dx scores categorized as low risk (0-18), intermediate risk (19-25), or high risk (26-100), as well as recurrence and overall survival. RESULTS: Of 1711 patients, 91 met ultra-low-risk eligibility criteria with available Oncotype Dx results. The median age was 70 years with a median follow-up of 5.1 years, and no patients received chemotherapy. Only 1 patient (1.1%) had a high-risk Oncotype Dx score of ≥26, while 12 (13.2%) had intermediate scores and 78 (85.7%) were low risk. Five-year local control and overall survival were 100% and 93%, respectively. Ten non-breast cancer deaths occurred, and no patients developed distant metastases. CONCLUSION: We describe a pragmatic method using common clinical and pathological features to define an ultra-low-risk cohort. Older luminal A patients with favorable pathology have a very low probability of receiving a high-risk Oncotype Dx score and demonstrate an excellent prognosis with standard adjuvant therapy.