Is there a role for the oncotype DX breast recurrence score genomic assay in estrogen receptor-low positive breast cancer?

Abstract

564 Background: The Oncotype DX Breast Recurrence Score assay is widely used in estrogen receptor (ER)-positive breast cancer patients to help determine the potential benefit of chemotherapy. However, little is known about the value of the test in breast cancer patients who have ER-low positive (1-10%) cancers. The purpose of this study was to determine the potential utility of the Oncotype test for these patients by describing the range of Recurrence Score (RS) results and patient outcomes. Methods: Patients treated between 8/2011-8/2020 for primary non-metastatic breast cancer that was ER-low positive (10%) and HER2-negative in whom tissue from their surgical excision specimen was available to perform the Oncotype DX assay were identified. Clinicopathologic characteristics were abstracted from patient charts, and the RS result was determined. Results: 38 women with ER-low positive breast cancer and available tissue were identified. The median age was 56.5 (range 36-94); 34 patients were Caucasian, 2 Black, 1 Asian and 1 Hispanic. Thirty-seven patients underwent surgery as their initial intervention and 1 received neoadjuvant chemotherapy. The final pathologic anatomic stage was IA in 26 (68.4%), IB in 10 (26.3%) and IIA in 2 (5.3%); the pathologic nodal status was pN0 in 24 (63.2%), pN0i+ in 3 (7.9%), pN1mi in 1 (2.6%), pN1 in 6 (15.8%) and pNx in 4 (10.5%). The average and median RS was 49 with a range of 23-72; only 2 patients had a RS 25. One patient with RS = 24 was a 64yo with pT1cN0 disease who received chemotherapy + endocrine therapy therefore could potentially have been spared chemotherapy based on the RS result and the TAILORx trial data. Six patients had previously had a RS determined on their diagnostic core biopsy (RS = 46, 58, 45, 47, 51 and 52); the RS on their surgical specimen was concordant (RS = 45, 54, 47, 48, 47, and 50). The ER status as determined by the Oncotype DX assay was positive for 8 (21%) patients. Adjuvant therapy included: chemotherapy and endocrine therapy in 13 (34.2%), chemotherapy alone in 13 (34.2%) and endocrine therapy alone in 4 (10.5%). 8 (21.1%) received no adjuvant therapy. After a median follow-up of 40 months (range 3-106), 3 patients have experienced a recurrence; all 3 had received chemotherapy. The 3-year recurrence free survival rate was 97.0% (95% CI: 96.9-97.1%). All 3 of these patients had a local recurrence; 2 also had a distant recurrence which they ultimately succumbed to. The 3-year disease-specific survival rate was also 97.0% (95% CI: 96.9-97.1%). Conclusions: The majority of the patients with low ER+/HER2- breast cancer had RS > 25 suggesting these tumors are high-risk, more similar to ER- disease. The RS result is of limited utility in ER-low positive patients, as these data indicate that most would benefit from chemotherapy.