- Oncotype DX testing is reimbursed in Israel for node-negative and node-positive (N1+; up to 3 positive nodes including micrometastases), estrogen receptor positive (ER+), breast cancer patients. This retrospective study evaluated the impact of Oncotype DX testing on treatment decisions in N1+/ER+ breast cancer patients. To this end, we compared treatments for all N+ patients for whom testing had been ordered with treatments for patients with similar characteristics where the test had not been available. The retrospective analysis included 951 patients (282 Oncotype DX, 669 controls), all of whom received endocrine therapy with or without chemotherapy. In Oncotype DX patients, 7.1, 37.0, and 100 % of those with low, intermediate, and high Recurrence Score results (Oncotype DX summary score) received chemotherapy, respectively (P < 0.0001, all comparisons). Chemotherapy use was lower in Oncotype DX patients versus controls (24.5 vs. 70.1 %). In a multivariate logistic regression analysis in which the probability of receiving chemotherapy was modeled as a function of Oncotype DX testing, age, tumor size, tumor grade, nodal status, and the interactions between Oncotype DX testing and the other covariates, Oncotype DX testing was associated with significantly lower odds of receiving chemotherapy (odds ratio 0.16; 95 % CI 0.11-0.24; P < 0.0001). In summary, our findings suggest that Oncotype DX testing has a significant impact on reducing chemotherapy use in N1+/ER+ breast cancer patients in Israel.