Oncotype Dx Breast Cancer Assay in Older Patients: A Real Life Cohort.

INTRODUCTION: The Oncotype DX Breast Recurrence Score test was designed for HR+, HER2- early breast cancer (eBC) to assist in the decision-making process for de-escalating adjuvant chemotherapy (CT). Its validity and utility have been demonstrated prospectively across multiple studies, though data on older patients remain limited. METHODS: This prospective cohort study included patients over 70 years with eBC treated between 2018 and 2023 at Tenon Hospital, Paris, France. Characteristics of populations eligible for the test and those with RS ≤ or > 25 were collected, along with oncogeriatric assessment and treatments; statistical analysis was performed for IDFS and OS. RESULTS: Of the 365 patients > 70 years, mean age was 77.6 years (range 70-96), with 84.4% diagnosed with HR+/HER2- eBC. Oncotype DX testing was performed in 85 patients (27.9% of HR+/HER2- eBC), revealing a Recurrence Score (RS) result > 25 in 14 patients (15%). The RS > 25 group had more grade 3 tumors, more pT2 tumors, and a higher Ki67 > 20%. In the RS > 25 group, 9 patients (64%) had oncogeriatric consultations, and 7 (50%) started the recommended adjuvant CT. Four patients received taxane-cyclophosphamide (TC) and 3 adriamycin-cyclophosphamide-taxane (AC-T), with 2 discontinuing due to taxane-induced neuropathy. Median IDFS was significantly lower in the RS > 25 group (p = 0.0023), with 4 of 5 recurrences occurring in patients who did not receive adjuvant CT. OS showed no significant difference by RS group (p = 0.87). CONCLUSION: This observational study highlights that the Oncotype DX test supports therapeutic de-escalation in patients with RS ≤ 25 and serves as a prognostic marker. Oncogeriatric evaluations are essential to guide adjuvant treatments in older breast cancer patients prior to using genomic signatures.