[255] Invasive Lobular Carcinoma and Oncotype Dx®: Impact of Pathology and Recurrence Score on Treatment Plan

Dara S Ross, Lanie C Galman, Jeff Catalano, Lee K Tan. Memorial Sloan-Kettering Cancer Center, New York

Background: Oncotype Dx® Breast Cancer Assay is a 21-gene assay that predicts whether certain patients with ER-positive breast cancer will benefit from chemotherapy. The goal of this project is to examine the impact of pathology and Oncotype Dx® Recurrence Score (RS) on the treatment plan for invasive lobular carcinoma (ILC).
Design: A search of the 2008-2011 pathology database was performed for cases of ILC submitted for Oncotype Dx® testing. The pathology, test results and treatment regimen for each patient was obtained. The histopathologic features of the tumors were recorded as were the results of their Oncotype Dx® RS. The latter was categorized into different risk categories based on the guidelines set forth by Oncotype Dx®: low risk (LR) <18, intermediate risk (IR) 18-30, high risk (HR) >30.
Results: A total of 1489 specimens were sent for Oncotype Dx® testing during the study period. Of these, 135 (9%) cases were classified as ILC. The age of the patients, tumor size and subtype, nodal status, Oncotype Dx® RS and treatment for the 3 risk groups are summarized in Table 1. The overall mean age was 58 years-old (range 34-79) and the overall mean tumor size was 1.6 cm (range 0.3-4.3 cm). The histology of the ILC was classical (n=108, 80%), pleomorphic (n=13, 10%), classical and pleomorphic (n=14, 10%). Twelve (9%) out of 133 patients that had axillary lymph node (LN) sampling had metastases (range 1-2 positive LN). All tumors were Her-2/neu negative by immunohistochemistry. The overall mean Oncotype Dx® RS was 16 (range 5-33), with the following distribution: LR 85 (63%), IR 48 (36%), HR 2 (1%). No patients with classical or mixed type ILC or with LN metastases were classified as HR. Two (15%) out of 13 pleomorphic ILC were in the HR category with scores of 31 and 33. Forty-two (31%) patients received chemotherapy (CT), 108 (80%) hormone therapy (HT) and 72 (53%) radiation therapy (RT).

ILC Characteristics
 LR (<18)IR (18-30)HR (>30)
N (total 135)85482
Age (yrs)57 (34-79)59 (45-77)69 (61-76)
Tumor Size (cm)1.7 (0.5-4.3)1.4 (0.3-3.6)1.8 (1.2-2.4)
Classical & Pleomorphic1040
LN Metastasis930
Recurrence Score13 (5-17)21 (18-29)32 (31-33)

Conclusions: 1) Regardless of subtype, 99% of ILC are in the LR/IR categories. 2) The clinical decision for administering CT in our study population was not based on Oncotype Dx® RS but determined by clinicopathologic variables. 3) Oncotype Dx testing does not provide additional predictive information for clinical management of patients with ILC.
Category: Breast

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 8, Tuesday Afternoon


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