Are we Overtreating Hormone Receptor Positive Breast Cancer with Neoadjuvant Chemotherapy? Role of OncotypeDx® for Hormone Receptor Positive Patients Undergoing Neoadjuvant Chemotherapy

Background The utilization of OncotypeDx in the setting of neoadjuvant chemotherapy (NCT) is not well defined. The objective of this study was to determine what proportion of hormone receptor (HR)-positive patients undergoing NCT would not benefit from chemotherapy based on OncotypeDx recurrence scores (RS) and predictors of a high RS as defined by the TAILORx trial. Methods The National Cancer Data Base was used to identify patients with unilateral clinical stage I-III HR+/Her2- breast cancer who had an OncotypeDx score and who had undergone NCT. Patients undergoing adjuvant chemotherapy were used as a comparison group. Results Of 307,666 patients, 41.8% had testing with OncotypeDx. Of these, 76.6% had no chemotherapy, 22.3% adjuvant chemotherapy, and 1.1% NCT. OncotypeDx testing in NCT patients increased from 4.9% in 2010 to 8.2% in 2015. Of NCT patients with OncotypeDx testing, 11.6% had RS < 11, 44.4% RS 11-25, and 43.9% RS > 25. In patients age <= 50 years, 14.5% had RS < 11, 12.4% RS 11-15, 31.4% RS 16-25, and 41.7% RS > 25. Predictors of RS > 25 on multivariable analysis included grade 3 tumors (odds ratio [OR] 3.83) and PR-negative tumors (OR 5.26) but not clinical T or N stage (p > 0.05). Conclusions More than half of patients with OncotypeDx testing are being overtreated with NCT, and a third of younger patients are being overtreated. Predictors of a high RS are reliably available at core biopsy, suggesting an application of OncotypeDx in determining the need for NCT for some HR-positive breast cancers.