Correlation between postoperative treatment selection and prognosis determined using the Oncotype DX® test data: a retrospective multicenter study in Japan.

PURPOSE: Oncotype DX® is a frequently used multigene assay for hormone receptor-positive breast cancers. However, limited evidence is available regarding its application in Japan owing to the lack of insurance coverage. Therefore, we conducted this large-scale, retrospective study by collecting data from nine Japanese institutes and assessed postoperative treatment choice and prognosis by using Oncotype DX®.

METHODS: Six hundred thirty-two patients who underwent breast surgery and whose recurrence score (RS) data were available were included. They were divided into RS 0-25 and RS ≥ 26 groups. The groups were compared in terms of clinicopathological factors, treatment options, and prognosis.

RESULTS: After the median follow-up period of 10.1 years, the disease-free survival (DFS) rates were significantly better in the RS 0-25 group (p = 0.02). Per the recurrent event type, there was no significant intergroup difference in locoregional recurrence (p = 0.139). However, a trend toward better distant DFS was observed in the RS 0-25 group (p = 0.08). Overall survival was also significantly better in this group (p = 0.027). Considering chemotherapy use, DFS worsened among chemotherapy-treated patients with an RS of 0-25 and those with an RS ≥ 26 who did not receive chemotherapy (p < 0.001). Seven (1.35%) chemotherapy-treated patients with an RS of 0-25 showed disease recurrence.

CONCLUSIONS: This study presents the largest database-derived prognostic data in Japanese patients, utilizing the Oncotype DX® treatment selection. Further studies are needed to determine the impact on treatment choice, considering the clinical risk, and the need for additional postoperative treatment.