Prognosis of ER-positive, HER2-negative postmenopausal early breast cancer patients based on response to neoadjuvant endocrine therapy and multigene assay results: findings from the NEOS trial

BACKGROUND: We previously reported the 21-gene Oncotype DX® assay results from TransNEOS in patients enrolled in the phase 3 NEOS trial. However, the association between assay results and long-term prognosis has remained unclear. METHODS: Of the 296 patients registered in TransNEOS, 226 patients were enrolled in this study. Multigene assay results were categorized into three groups based on Recurrence Score® (RS): RS low < 11, RS intermediate 11-25, RS high > 25. Kaplan-Meier methods evaluated the association between RS results and DDFS and OS across treatments and clinical response to neoadjuvant endocrine treatment (NET). RESULTS: The clinical efficacy of NET was judged as CR, PR, and SD in 4 (1.8%), 113 (50%), and 109 (48.2%) patients, respectively. In the RS low and intermediate groups, no statistically significant difference in DDFS or OS was observed between the endocrine therapy (ET) alone group and the chemoendocrine therapy (CT + ET) group. In the RS high group, OS was significantly lower in the ET group compared to the CT + ET group (p = 0.037). Among patients in the RS high group who achieved CR + PR response to NET, there was no significant difference in OS between the CT + ET group and the ET alone group (p = 0.25). However, the number of events was limited, and the study may have been underpowered to detect a meaningful difference. CONCLUSIONS: The need for chemotherapy in postmenopausal HR + , HER2- breast cancer patients might be further informed by integrating the results of the Oncotype DX test with the response to NET.