The 21-gene Recurrence Score (RS) (Oncotype DX®; Genomic Health, Redwood City, CA) is the most valid and reliable multigene assay to predict prognosis or response to chemotherapy in hormone receptor-positive invasive breast cancer patients. In Japan, however, the test is not frequently used because of its expensive and no coverage by national insurance. We have developed a model to predict low recurrence risk (low-RS) using 220 patient data from St. Luke’s International Hospital, Tokyo, Japan (presented at San Antonio Breast Cancer Symposium 2016). The model with 4 factors, including the histologic type (invasive ductal or lobular), the expression level of PgR (Allred score 7,8 or 24), and the presence of lymphovascular invasion, showed that 92% of patients with high PgR positive and Ki67 < 24 could be classified as low-RS with an AUC of 0.843 (95%CI: 0.790-0.896). The aim of this study was to validate our prediction model with external patient data.
A validation set of clinicopathological data from 77 patients who had primary invasive carcinoma surgically resected and underwent OncotypeDx® was obtained from Showa University, school of medicine, Tokyo, Japan.
According to the distribution of 4 factors between two cohorts, there was a significant difference in Ki67 level (
Regardless of the inconsistency of Ki67 level between institutes, our model could provide useful information to predict low-RS in hormone receptor-positive invasive breast cancer patients. This model would be helpful to select patients who had better apply OncotypeDX®.
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All authors have declared no conflicts of interest.