Background: The Oncotype DX Breast Recurrence Score (ODX) assay is a 21-gene assay validated in hormone receptor-positive, HER2 negative invasive breast cancer (BC) to predict chemotherapy benefit and risk of distant recurrence at 10 years regardless of node status and is also a strong predictor of mortality. ODX can minimize the misuse of chemotherapy, financial burden, and improve clinical outcomes. ODX is not widely used in Ecuador due to socioeconomic and healthcare access disparities; instead, many physicians stratify patients' risk according to clinicopathological and immunohistochemical features. We aim to compare the differences between ODX and two of the most common stratification clinical tools: Predict Score (PS) and Nottingham prognostic index (NPI). Methods: Retrospective analysis of women with early BC who underwent ODX testing in Ecuador from May 2020 to January 2023. Inclusion criteria: early BC (T1-T3 / N0-N1a); estrogen receptor (ER) positive; HER2 negative by immunohistochemistry; and available data of tumor size, grade, lymph node status, and Ki67 proliferation index. Exclusion criteria: patients with recurrent BC, incomplete pathology, or immunohistochemistry data. PS and NPI were calculated using online tools. The correlation between PS, NPI, and ODX scores was analyzed using Spearman's correlation coefficient in SPSS. Results: 77 patients underwent ODX testing, of which 58 patients (mean age 55 years old) met the inclusion criteria. Invasive breast carcinoma not otherwise specified was the most common type (48 patients (82%). Risk scores generated by PS correlated strongly with NPI for all patients (r=0.47; p ≤ 0.001). A strong correlation was also found between ODX and NPI (0.79, p<0.027). Risk scores were then stratified by patient risk category. For low-risk patients, 68% of correspondence between ODX and PS was found, and 98% between ODX and NPI. Intermediate-risk patients showed a correspondence between ODX and PS of 5% and 9% for ODX and NPI. High-risk patients showed a correspondence of 50% between ODX and PS and 17% between ODX and NPI. Conclusions: ODX risk recurrence for low-risk patients is highly correlated with PS and NPI. For Intermediate and high-risk patients determined by PS and NPI, ODX testing provided valuable and prognostic information and should be considered to guide adjuvant treatment.

Pts: points.