Can Factors Evaluated in the Routine Pathologic Evaluation of Lymph Node-Negative Estrogen Receptor-Positive Stage I or II Invasive Breast Cancer Be Used To Predict the Oncotype DX Assay Recurrence Score?
J Auerbach, S Fineberg. Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY
Background: Oncotype Dx is a commercially available multigene RT-PCR assay which is used to quantify the risk of breast cancer recurrence in patients with stage I or II estrogen receptor-positive lymph node (LN) negative invasive breast cancer who will be treated with tamoxifen. Patients with high recurrence score (RS) derive a large benefit from cytotoxic chemotherapy while those with a low RS derive little if any benefit from chemotherapy. This study is to determine if progesterone receptor (PR) evaluation or mitotic count score, which are part of the routine pathologic evaluation of all breast cancers, could predict Oncotype Dx assay RS results.
Design: Thirty-seven cases of LN negative, ER positive invasive breast cancer were identified where both results of an Oncotype Dx assay and slides were available for review. In all cases, the slide from the block sent for Oncotype Dx was reviewed and evaluated using the Nottingham grading system. ER, PR and Her2/Neu status was available. The Oncotype RS was obtained with the number and category of risk as follows: <18 (low), 18-30 (intermediate) and >30 (high).
Results: Of the 37 patients with BC in the study, 22 were low, 13 were intermediate and 2 were high risk for BC recurrence according to the RS guidelines. All cases were ER positive. There were 7 PR negative cases and in these cases the RS was 18, 20, 20, 23, 30, 34 and 40 respectively. There were no low risk RS among the PR negative cases. Thirty patients were PR positive and of those 23 had a RS of 17 or less. There were only 5 cases with a mitotic count score of 3 and in these cases the RS was 16,20,23,34 and 49 respectively. In 2 cases with RS of 34 and 49, mitotic count score was 3 and PR was negative. In 4 patients with a RS of greater than 17 both PR was positive and the mitotic count score was less than 3.
Conclusions: In our study, breast cancer cases with both a mitotic count score less than 3 and PR positivity, we could not accurately predict RS. However, cases with an invasive breast cancer showing absence of progesterone receptor and/or mitotic count of 3 can be predicted to have an intermediate or high RS. If the goal of the oncologist is to omit chemotherapy, the contribution of RS determination in this subset of patients (PR negative and/or mitotic count score of 3) may be low.
Wednesday, March 11, 2009 1:00 PM
Poster Session VI # 19, Wednesday Afternoon