Impact of Oncotype DX Recurrence Score on Treatment Decisions: Results of a Prospective Multicenter Study in Turkey

Introduction: Breast cancer is the most common malignancy among Turkish women and the rate of early stage disease is increasing. The Oncotype DX® 21-gene assay is predictive of distant recurrence in ER-positive, HER2-negative early breast cancer. We aimed to evaluate the impact of the Recurrence Score® (RS) on treatment decisions and physician perceptions in Turkey. We also studied correlations between RS and routine risk factors. Patients and Methods: Ten academic centers across Turkey participated in this prospective trial. Consecutive breast cancer patients with pT1-3, pN0-N1mic, ER-positive, and HER2-negative tumors were identified at multidisciplinary tumor conferences. The initial treatment decision was recorded before tumor blocks were sent to the central laboratory. Each case was brought back to tumor conference after receiving the RS result. Both pre- and post-RS treatment decisions and physician perceptions were recorded on questionnaire forms. Correlations between RS and classical risk factors were evaluated using univariate and multivariate analyses. Results: Ten centers enrolled a total of 165 patients. The median tumor size was 2 cm. Of 165 patients, 57% had low RS, 35% had intermediate RS, and 8% had high RS, respectively. The overall rate of change in treatment decision was 33%. Initially, chemotherapy followed by hormonal therapy (CT+HT) was recommended to 92 (56%) of all patients, which decreased to 61 (37%) patients post-RS assay (p<0.001). Multivariate analysis indicated that progesterone receptor (PR) and Ki-67 scores were significantly related to RS. Conclusion: Oncotype DX testing may provide meaningful additional information in carefully selected patients.