Prognostic analysis of three forms of Ki-67 in patients with breast cancer with non-pathological complete response before and after neoadjuvant systemic treatment.

BACKGROUND: Patients who do not achieve a pathological complete response (pCR) after neoadjuvant systemic treatment (NST) have a significantly worse prognosis. A reliable predictor of prognosis is required to further subdivide non-pCR patients. To date, the prognostic role in terms of disease-free survival (DFS) between the terminal index of Ki-67 after surgery (Ki-67T ) and the combination of the baseline Ki-67 at biopsy before NST (Ki-67B ) and the percentage change in Ki-67 before and after NST (Ki-67C ) has not been compared. AIM: This study aimed to explore the most useful form or combination of Ki-67 that can provide prognostic information to non-pCR patients. PATIENTS AND METHODS: We retrospectively reviewed 499 patients who were diagnosed with inoperable breast cancer between August 2013 and December 2020 and received NST with anthracycline plus taxane. RESULTS: Among all the patients, 335 did not achieve pCR (with a follow-up period of ≥1 year). The median follow-up duration was 36 months. The optimal cutoff value of Ki-67C to predict a DFS was 30%. A significantly worse DFS was observed in patients with a low Ki-67C (p < 0.001). In addition, the exploratory subgroup analysis showed relatively good internal consistency. Ki-67C and Ki-67T were considered as independent risk factors for DFS (both p < 0.001). The forecasting model combining Ki-67B and Ki-67C showed a significantly higher area under the curve at years 3 and 5 than Ki-67T (p = 0.029 and p = 0.022, respectively). CONCLUSIONS: Ki-67C and Ki-67T were good independent predictors of DFS, whereas Ki-67B was a slightly inferior predictor. The combination of Ki-67B and Ki-67C is superior to Ki-67T for predicting DFS, especially at longer follow-ups. Regarding clinical application, this combination could be used as a novel indicator for predicting DFS to more clearly identify high-risk patients.