OncotypeDX Testing Does Not Benefit Patients with Estrogen and Progesterone Receptor Positive Grade 1 Breast Cancers: A TAILORx Validated Study.

Background & objectives: We previously described a predictive AAMC model that identifies patients (grade 1, hormonepositive) who would not benefit from OncotypeDX testing. The purpose of this study was to validate the AAMC model by assessing distant recurrence-free interval (DRFI) and invasive disease-free survival (IDFS) using TAILORx clinical trial data.

Materials & methods: We retrospectively analyzed TAILORx trial data and categorized patients based on the AAMC model. AAMC low-risk patients are those with grade 1 and hormone-positive tumors. Kaplan-Meier curves examined DRFI and IDFS.

Results: Of the 9195 cases, 2246 (24.4%) were identified by AAMC as low-risk. Among these AAMC low-risk patients, 55.2% had Recurrence Score (RS) 0-15, 42.3% had RS 15-25, and 2.4% had RS > 25. The 10-year DRFI did not differ for those who received adjuvant chemotherapy versus those who did not (98% vs. 96%, log-rank p = 0.46). Similarly, IDFS was comparable between those who received adjuvant chemotherapy and those that did not (86% vs. 86%, log-rank p = 0.66). Only 2.4% of AAMC low-risk patients were categorized as high-risk (RS > 25). A sensitivity analysis of this discordant group, wherein those with RS > 25 were re-classified into the no-chemotherapy group and assumed to have experienced recurrences at the rate expected without chemotherapy, did not find any difference in DRFI between those who received adjuvant chemotherapy and those who did not (log-rank p = 0.16).

Conclusion: OncotypeDX testing does not benefit AAMC low-risk patients with hormone-positive grade 1 tumors. Based on these data, 1 in 4 TAILORx participants would not need OncotypeDX testing.