Abstract
PURPOSE: To determine whether multiple primary breast cancers have similar genetic profiles, specifically Oncotype Dx Recurrence Scores, and whether obtaining Oncotype Dx on each primary breast cancer affects chemotherapy recommendations. METHODS: A database of patients with hormone receptor-positive, lymph node-negative, breast cancer was created for those tumors that were sent for Oncotype Dx testing from the University of Michigan Health System from 1/24/2005 to 2/25/2013. Retrospective chart review abstracted details of tumor location, histopathology, distance between tumors, Oncotype Dx results, and chemotherapy recommendations. RESULTS: Six hundred and sixty-six patients for whom Oncotype Dx testing was sent were identified, with 22 patients having multiple breast tumor specimens sent. Of the 22 patients who had multiple samples sent for analysis, chemotherapy recommendations were changed in 6 of 22 patients (27%) based on significant differences in Oncotype Dx Recurrence Scores. Qualitatively, there seems to be a greater difference in genetic profile in tumors appearing simultaneously on different breasts when compared to multiple tumors on the same breast. There was no association between distance between tumors and difference in Oncotype Dx scores for tumors on the same breast. CONCLUSIONS: Oncotype Dx testing on multiple primary breast cancers altered management in regards to chemotherapy recommendations and should be considered for multiple primary breast cancers.