Survival outcome and reduction rate of Ki-67 between pre- and post-neoadjuvant chemotherapy in breast cancer patients with non-pCR

The research question of this investigation is whether the reduction rate of Ki-67 after neoadjuvant chemotherapy (NAC) could indicate a survival in patients with non-pCR. A total of 455 patients had received NAC, and subsequent surgery was analyzed retrospectively. Patients with non-pCR were divided into three subgroups according to Ki-67 change: High-reduction (the absolute value of Ki-67 was reduced by >80 % compared with that prior to NAC), Low-reduction (the absolute value of Ki-67 was reduced by 0–80 % compared with that prior to NAC), and Increase group (the absolute value of Ki-67 was increased compared with that prior to NAC). The relapse-free survival (RFS) rates were compared among subgroups. pCR was achieved in 93 patients (20.4 %). In patients with non-pCR, the median reduction rate of Ki-67 was 60 %. A total of 15 % of patients were in the High-reduction, 63 % in the Low-reduction, and 22 % in the Increase group. The median follow-up period was 64.5 months. The 5-year RFS rates among the three groups were significantly different (p < 0.0001), and the differences were also observed in the HER2 (p = 0.033), triple-negative (p = 0.034), and luminal-like subtypes (p = 0.001). Patients in the High-reduction group showed comparable RFS to that of patients with pCR (p = 0.363). In patients with non-pCR, the reduction rate of Ki-67 after NAC significantly predicted RFS regardless of cancer subtypes. Therefore, patients who are non-pCR but who achieve a high reduction of Ki-67 can be expected to have a favorable prognosis similar to that of patients with pCR.