Abstract P2-07-11: Prediction of the Oncotype Dx recurrence score (RS) from clinicopathologic factors

Abstract

Abstract Background: The Oncotype Dx assay is currently used as an aid to therapeutic decisions for the adjuvant treatment of women with ER-positive, Her2-negative, lymph node-negative or -micrometastatic breast cancer. The recently reported TAILORx study showed that no or minimal benefit is derived from adjuvant chemotherapy in patients with an Oncotype Dx Recurrence Score (RS) of 25 or less. Methods: Charts of breast cancer patients that had the Oncotype Dx test in our cancer center in a nine-year period were reviewed. Data on demographic, and cancer-specific characteristics of the included patients were extracted. Predicted disease recurrence from the Oncotype Dx test was recorded and correlated with select clinicopathologic characteristics. Results: Two hundred and thirty patients with ER-positive, Her2-negative, lymph node-negative or micrometastatic breast cancer were included. Mean age was 65 years-old (SD 9.9). Two hundred and three patients (88.3%) were post-menopausal and one hundred and thirty-three patients (57.8%) were 65 years-old or older. Two hundred and nine patients (90.9%) had lymph node-negative disease. Oncotype Dx recurrence score was low (<11) in sixty-four patients (27.8%), intermediate (11-25) in one hundred and forty patients (60.9%) and high (>25) in twenty-six patients (11.3%). High tumor grade and low progesterone receptor (PR) staining by IHC were the two clinicopathologic factors most associated with a high Oncotype Dx RS (x2 test p <0.00001 and Fisher's exact test p <0.0001). A predictive index (PI) was constructed, assigning one point each for grade 3 and PR staining in 20% or less of tumor cells. A PI of 0 was observed in one hundred and thirty-eight patients (60%), a PI of 1 was observed in seventy-one patients (30.9%), and a PI of 2 was observed in twenty-one patients (9.1%). One hundred and thirty-four patients (97.1%) with a PI of 0 had a RS of 25 or less. Patients with a PI of 1 and 2 had a RS of >25 in 12.7% and 61.9% of cases, respectively. Conclusion: The PI based on tumor grade and PR we propose is a simple predictor of Oncotype Dx RS. 97.1% of patients with a grade 1 or 2 tumor and PR positivity in >20% of tumor cells had a RS of 25 or less. The Oncotype Dx test and its associated cost can therefore be avoided in these patients, especially in low-resource settings. Citation Format: Voutsadakis IA, Thibodeau S, Reed M. Prediction of the Oncotype Dx recurrence score (RS) from clinicopathologic factors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-07-11.