Is Oncotype DX Testing Necessary For Patients With Node Negative, Low-Grade Invasive Ductal Breast Carcinoma?

Introduction/Objective Oncotype DX (Genomic Health/Exact Sciences, Redwood City, CA) is a 21-gene expression test that is used to predict the risk of recurrence following hormonal therapy and adjuvant chemotherapy (CT) benefit for patients with early-stage, ER-positive and HER2-negative invasive breast carcinoma (IBC). Testing is performed on formalin-fixed, paraffin-embedded tumor tissue from patients that are either lymph node (LN) negative, have micro- metastases, or 1-3 positive LNs. For years pathologists have studied traditional prognostic features of IBC (tumor grade, size, and LN status), as well as biomarker testing results (ER, PR, HER2, and Ki-67), in an effort to identify surrogate equations that could help identify patients that would benefit from CT. The “TAILORx” clinical trial, performed to study CT benefit in patients with midrange recurrence scores (11-25), has shown that the majority of these patients do not derive benefit from CT. Post-TAILORx, we have observed that only a small subset of our node- negative patients who were tested showed a benefit for CT. Following the examination of Oncotype DX results from testing performed on our patients, we hypothesized that overall tumor grade (Nottingham) might predict which patients with invasive ductal breast carcinoma (IDBC) do not require Oncotype DX testing; therefore, eliminating the need for Oncotype DX testing. Methods/Case Report We reviewed the surgical pathology reports and Oncotype DX reports for 251 patients with node-negative disease who underwent surgery at our institution from September 2019 through June 2021. All excisional tumors sent for Oncotype DX testing were ER-positive (Allred score ≥6/8) and HER2-negative by IHC and/or FISH. Results (if a Case Study enter NA) Oncotype DX recurrence scores ranged from 0-65. A benefit for CT was seen in 10.4% (26/251) of the patients with node-negative IDBC. A benefit for CT was seen in 6.1% (7/114) of patients with an overall tumor grade of II and 44.2% (19/43) of patients with an overall grade of III. No patients (0/94) with IDBC and an overall tumor grade of I showed a benefit for CT. Conclusion In the post-TAILORx era, patients with ER-positive (Allred ≥6/8), HER2-negative IDBC, who are node- negative and show an overall tumor grade of I, apparently do not require Oncotype DX testing. Additional studies from other institutions are needed to confirm our observation.