Histopathologic variables predict Oncotype DX™ Recurrence Score

Oncotype DX is a commercially available reverse transcriptase-polymerase chain reaction based assay that provides a Recurrence Score (RS) and has been shown to provide prognostic and predictive information in estrogen receptor-positive lymph node-negative breast cancers. Independent studies of its utility in routine practice are lacking. Slides and surgical pathology reports from 42 cases of breast carcinomas evaluated by Oncotype DX were retrospectively reviewed to determine patient age, tumor size, histologic grade, estrogen and progesterone receptor (ER and PR) and ERBB2 (HER-2/neu) data, with ER and PR reported as a semi-quantitative score reflecting both intensity of staining and proportion of positive cells. We show here that Recurrence Score is significantly correlated with tubule formation, nuclear grade, mitotic count, ER immunohistochemical score, PR immunohistochemical score, and HER-2/neu status, and that the equation RS=13.424+5.420 (nuclear grade) +5.538 (mitotic count) -0.045 (ER immunohistochemical score) -0.030 (PR immunohistochemical score) +9.486 (HER-2/neu) predicts the Recurrence Score with an R2 of 0.66, indicating that the full model accounts for 66% of the data variability. Although the Oncotype DX Recurrence Score holds potential, further validation of its independent value beyond that of histopathologic analysis is necessary before it can be implemented in clinical decision making.