Progesterone Receptor and Ki-67 Immunohistochemistry Predict Oncotype Dx® Recurrence Score in Lymph Node Negative and Positive Breast Cancers
Laura S Spruill, J R McEvoy. Medical University of South Carolina, Charleston, SC; Roper St. Francis Heathcare, Charleston, SC
Background: Oncotype Dx® is a proprietary molecular assay that detects the expression level of RNA associated with behavior of invasive breast cancer. Results are reported as a Recurrence Score (RS) and stratified into low, intermediate, and high risks groups which theoretically correlate with risk of recurrence at 10 years after surgical treatment only. RS may used by oncologists as a tool to guide initiation of chemotherapy. The ongoing prospective TAILORx trial utilizes a modification of the standard RS risk stratification values which expands the number of patients in the intermediate group.
Design: Our objective was twofold: 1) to test whether routinely performed histology and immunohistochemical studies could be used to predict the RS in a cohort of lymph node negative and lymph node positive patients, and 2) to assess the prediction of recurrence using both the standard RS and the modified TAILORx RS. H&E stained slides were used to assess morphology including the components of the Nottingham combined histologic grade. Immunohistochemistry was used to assess hormone receptor expression, Ki-67 positivity, and Her-2/neu expression.
Results: The most recent 92 cases with invasive carcinoma and Oncotype DX® results were evaluated. Of those, 69 cases were node negative and 23 were node positive. Using the standard RS, 56 cases were low risk, 26 were intermediate risk, and 10 were high risk. Using the modified TAILORx stratification, 19 cases were low risk, 57 were intermediate risk, and 16 were high risk. Bivariate analysis demonstrated that PR status, Nottingham grade, nuclear score, mitotic rate, and Ki-67% were significantly associated with RS using both the standard and modified TAILORx risk stratifications. However, multivariate logistic regression analysis demonstrated that only a positive PR status and low Ki-67% were predictive of a low RS using the standard risk stratification. None of the variables remained predictive of RS when the modified TAILORx values were applied.
Conclusions: Our study demonstrates that PR status and Ki-67% are predictive of Oncotype DX® RS values using the currently clinically applicable standard risk stratification in a cohort of lymph node negative and lymph node positive patients.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 12, Tuesday Afternoon