Changes in Recurrence Score by neoadjuvant endocrine therapy of breast cancer and their prognostic implication

Background Neoadjuvant endocrine therapy (NET) can improve surgical outcomes in postmenopausal patients with hormone receptor-positive breast cancer. The Ki67 labelling index after NET has a better prognostic power than that at baseline. However, it remains unknown whether a multigene assay with post-treatment samples could predict the prognosis better than that with pretreatment samples. Methods The prognostic value of the multigene assay Oncotype DX Recurrence Score (RS) was investigated using pretreatment and post-treatment samples from a multicentre NET trial, JFMC34-0601 (UMIN C000000345), where exemestane was given at 25 mg/day for 24 weeks. Results Both pretreatment and post-treatment RSs were significantly associated with disease-free survival (DFS) (p=0.005 and 0.002, respectively). The combination of pretreatment and post-treatment RSs was also a predictor of DFS (p=0.002) and superior to preoperative endocrine prognostic index (PEPI). Furthermore, combined RS was the only independent prognostic factor in the multivariate analysis among the three RSs (p=0.04). In addition, combined RS could differentiate early recurrence in the high-risk group from mid/late recurrence in the intermediate-risk group, suggesting possible differential treatment strategies based on the risk categories indicated by the combined RS. Conclusions The combination of pretreatment and post-treatment RSs could provide pivotal information for predicting DFS and differentiating early recurrence in the high-risk group from mid/late recurrence in the intermediate-risk group in patients with hormone receptor-positive breast cancer. A larger study is required to validate the results.