Distribution of oncotype recurrence scores in invasive lobular carcinomas.

Abstract

e13025 Background: Invasive lobular carcinomas (ILC) account for approximately 10-15% of all invasive breast cancers, with the majority of cases presenting as ER/PR positive and HER2 negative. As a result, they often exhibit more robust responses to hormone therapy than adjuvant chemotherapy. Oncotype Recurrence Score (RS) RS is a 21-gene assay used to predict the rate of distant recurrence and response to chemotherapy in women with node-negative, hormone-positive breast cancers. Limited evidence exists regarding oncotype scores for ILC tumors, thus the aim of this study was to examine the distribution and risk stratification of Oncotype RS in ILC tumors. Methods: We analyzed patient and tumor characteristics of 492 patients- 417 (85%) IDC (intraductal carcinoma) and 75 (15%) ILC. Chi-square tests and Wilcoxon rank-sum tests were used to compare categorical and numerical outcomes, respectively. Results: No significant difference was found between IDC and ILC in terms of age and ER/PR positivity. The RS raw scores were also not significantly different between the two groups (both had median scores of 16). ILC patients were significantly more likely to be in the lower RS risk groups using the traditional (Paik) cutoff than ILC patients (61%, 39% and 0% in low, medium and high-risk groups as compared to 57%, 33% and 10% in IDC, p < 0.01). Of 417 patients with IDC, there were 16 recurrences (4%) with a median time from diagnosis to recurrence of 43 months (IQR: 28 Ð 58 months), while 1 in 75 ILC patients had recurrence at 50 months. Conclusions: Oncotype RS scores have the potential to guide treatment decisions in node-negative breast cancers. Though mean RS were similar between ILC and IDC patients, ILC were more likely to be distributed in low-risk groups. Our study was limited by a small sample size and a single ILC recurrence. Further research is needed to determine oncotype RS and recurrence rates. Future studies with longer term follow up can help better elucidate patterns of recurrence scores and recurrence rates based on histologic tumor type. [Table: see text]