Results of Oncotype DX in early-stage invasive lobular carcinoma.

Abstract

59 Background: The Oncotype DX (ODX) genomic assay has been used since 2004 to estimate prognosis and guide adjuvant treatment in patients with estrogen receptor-positive, node-negative invasive breast tumors. However, the impact of ODX assay testing in patients with invasive lobular carcinoma (ILC) has not been specifically reported. We describe our experience in patients with ILC who underwent ODX assay testing and how this affected adjuvant treatment. Methods: An IRB approved retrospective review was performed on all patients undergoing treatment for early stage, node-negative ILC from 2006-2011. All cases were reviewed by a single pathologist (GA) for verification of histology and subtype. The impact of ODX assay testing on treatment management was evaluated. Results: Thirty-nine patients underwent ODX genomic assay testing of early stage, node-negative ILC with a median age of 62 years. ILC tumor classification included classic (67%), pleomorphic (23%) and mixed (10%) subtypes with a median tumor size of 2.0 cm (0.6-6.0). Ninety-seven percent of tumors were estrogen receptor-positive, 74% progesterone receptor-positive. Median ODX recurrence score was 15 (0-34) with an ODX 10-yr risk of 10% (3-23). ODX risk classification was: Low (N=26), Intermediate (N=12), and High (N=1). There was no difference in ODX recurrence score or risk classification between ILC subtypes (p=0.52 and p=0.35, respectively). Adjuvant chemotherapy was used in 26% (TC N=8, AC N=1, FEC 100 N=1). Tumor size or ILC tumor subtype were not significant for adjuvant chemotherapy use while tumor grade (p=0.046), ODX recurrence score (22.8 vs 13.6, p<0.0001), ODX risk classification (p=0.009) and ODX 10 year risk (15.9 vs 9.0, p<0.0001) were significant. With a median follow up of 16.5 months, there were no recurrences or tumor-related deaths. Conclusions: ODX testing on early stage node-negative ILC may serve as a useful adjunct when counseling patients on the decision for adjuvant therapy. The long-term impact on recurrence or survival in patients with ILC who receive adjuvant chemotherapy based on ODX recurrence score remains undetermined and warrants further testing.