CLO21-019: Association Between Oncotype Dx Breast Recurrence Score® and Estrogen and Progesterone Receptor Status

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  • 1 Joan C. Edward School of Medicine at Marshall University, Huntington, WV

Background: The 21 gene assay Oncotype Dx Breast Recurrence Score (RS) is currently the standard of care to determine if adjuvant chemotherapy is needed in early stage hormone receptor positive, node negative, HER-2 negative breast cancer. In current NCCN guidelines, adjuvant chemotherapy is recommended for patients with an RS greater than 26 because patients with an RS less than 26 have no demonstrated benefit from adjuvant chemotherapy. We sought to evaluate the relationship between the RS and the percentage of estrogen/progesterone receptor (ER/PR) expression that might have potential as a surrogate measure when deciding on adjuvant chemotherapy. Methods: From years 2015 to 2019, we identified 301 patients from our cancer registry with early stage hormone receptor positive breast cancer and had oncotype DX testing performed. Based on the numerical score followed by NCCN to determine the indication of chemotherapy in this group of patients, we divided them to three groups: Group 1 (G1) with RS < 26; Group 2 (G2) with RS 26 – 30; and Group 3 (G3) with RS > 31. We also collected information on tumor size (cm), tumor grade, Nottingham score, and ki-67 percentage. We compared all continuous variables across RS groups using the Kruskal-Wallis rank test and individual between group comparisons using the Wilcoxon rank sum test. All statistical tests performed utilized a two-tailed p value of <0.05 with the Bonferroni correction for multiple comparisons. Results: Among 301 patients with early stage hormone receptor positive breast cancer, 89.1% were ductal, 7.9% lobular, and 2.9% mixed histology. Median age was 65, 60 and 63 for G1, G2, and G3, respectively (p = 0.41). Median estrogen receptor percentages were 93.4 (G1), 90.1 (G2), and 84.5 (G3) (p = 0.48 for G1 vs. G2; p = 0.01 for G1 vs. G3). Median progesterone receptor percentages were 79.1 (G1), 14.4 (G2), and 5.9 (G3) (p < 0.001 for G1 vs. G2 and G1 vs. G3). As expected, tumor grade, tumor size, and Nottingham score increased significantly from G1 to G3. Conclusion: We found a significant association between hormone receptor levels and Oncotype Dx recurrence score (RS) in patients with early stage hormone receptor positive breast cancer patients. Further study is needed to determine the predictive ability of hormone receptor levels and RS, both individually and in combination, on the outcomes of patients treated for early stage hormone receptor positive breast cancer.

Corresponding Author: Noman Ahmed Jang Khan, MD
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