An Analysis of Oncotype DX Recurrence Scores and Clinicopathologic Characteristics in Invasive Lobular Breast Cancer

The Oncotype DX breast cancer assay (Genomic Health, Redwood City, CA) is increasingly being used to guide treatment decisions for patients with early stage, hormone‐positive, Her‐2‐negative breast cancer. The utility of the Oncotype DX in decision making for treatment of invasive lobular carcinoma (ILC) has not been investigated as the results reported by Genomic Health are largely in a population with invasive ductal carcinoma (IDC). The authors hypothesized that the Oncotype DX recurrence score (RS) distribution for ILC is different than that for IDC. We performed a retrospective analysis of early stage breast cancer patients treated at Penn State Cancer Institute from 2001 to 2011 and identified 102 patients with ILC. We also pulled RS data from our institution's prospective registry of consecutive patients with early stage IDC treated during the same time period. Median follow‐up was 55 months. We found that the RS distribution for ILC differed significantly from that of IDC (p = 0.024). We also found a statistically significant difference in the RS distribution between the pure ILC and pleomorphic ILC subtypes (p = 0.027). The Oncotype DX RS distribution in ILC is unique, differing significantly from that in ductal carcinoma. Consequently, the clinical usefulness and cost‐effectiveness of the Oncotype DX in guiding treatment for ILC should be further investigated.