Oncotype Dx Testing In Early-Stage Node-Positive Breast Cancer And Impact On Chemotherapy Use At A Comprehensive Cancer Center.

549 Background: The 21-gene Oncotype DX Recurrence Score (RS) is widely used to guide adjuvant chemotherapy decisions in hormone receptor positive (HR+), HER2-negtive (HER2-), lymph node negative (LN-) breast cancer. It’s adoption in lymph node positive (LN+) disease remains controversial. In 2016, we implemented ‘reflex’ RS testing for patients ≤65 years with HR+/HER2- breast cancer including T1/T2 N1 (grade 1 or 2) tumors. Providers can also order Oncotype DX outside of reflex criteria. We sought to assess RS distribution and factors associated with chemotherapy use in HR+/HER2-/LN+ breast cancer patients at our center. Methods: Patients with non-metastatic HR+/HER2-/LN+ breast cancer who underwent primary surgery at our center were identified from our prospective database. We examined the distribution of low (RS < 18), intermediate (RS 18-30) and high (RS > 30) RS and identified characteristics for those who did not meet reflex criteria. A multinomial logistic regression model was performed to identify factors associated with chemotherapy receipt among all LN+ patients. Results: From 1/2016-3/2018, we identified 296 consecutive patients with HR+/HER2-/LN+ breast cancer. 200 (68%) patients had RS testing and 128 (64%) met reflex criteria. Reasons for not meeting RS reflex criteria included age > 65 (n = 35), grade III disease (n = 35) and N2/N3 tumors (n = 10). Among the 200 patients with RS, 122 (61%) had RS < 18, 67 (34%) had RS 18-30, and 11 (6%) had RS > 30. Only 68/200 (34%) patients with RS received chemotherapy as compared to 54/96 (56%) patients without RS (p = 0.0004). Compared to patients without RS testing, the odds of receiving chemotherapy were less with RS < 18 (OR = 0.46). The odds of receiving chemotherapy were greater with ≥3 positive LNs versus 1 positive LN (OR = 3.40). Conclusions: The majority of HR+/HER2-/LN+ patients undergoing upfront surgery at our center receive RS testing (200/296), with 122 (61%) resulting in low risk RS. Patients with low risk scores (RS < 18) were less likely to receive chemotherapy. While nodal involvement remains a common driver of chemotherapy use, our study demonstrates that RS testing provides clinically useful information in this population.