Context: Oncotype DX is a multigene reverse transcription-polymerase chain reaction assay used to quantify recurrence risk in patients with stage I or II estrogen receptor-positive, lymph node-negative invasive breast cancer. The results are reported as a Recurrence Score (RS). The 16 cancer genes evaluated include a proliferation set, hormone receptor set, and HER2 set. The activity of these genes is addressed by pathologic assessment of breast cancers.
Objective: To determine if factors evaluated in pathologic evaluation of breast cancer could be used to predict Oncotype DX results.
Design: We studied 138 cases of invasive breast cancer for which Oncotype DX results and pathology data were available. Grading was performed by using Nottingham grading system. For hormone receptor immunostaining, 10% nuclear staining was considered a positive result.
Results: Oncotype DX RS was low in 81 cases, intermediate in 44 cases, and high in 13 cases. All 6 cases with both a negative progesterone receptor (PR) and a mitotic count score of 3 had a high RS. All 12 cases with both a negative PR and a mitotic count score greater than 1 had either an intermediate or high RS. Although Nottingham grade, PR status, mitotic count score, tumor size, and nuclear grade were each significantly associated with RS, in bivariate analyses the only variables that remained independently predictive of an intermediate or high RS score in a multivariate logistic regression model were negative PR and mitotic count score greater than 1.
Conclusions: Our study suggests that a mitotic count score greater than 1 combined with a negative PR result, as determined by pathologic assessment, could serve as a marker for an intermediate or high Oncotype DX RS.