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.