High expression of post-treatment Ki-67 status is a risk factor for locoregional recurrence following breast-conserving surgery after neoadjuvant chemotherapy

IntroductionDuring the past decade, neoadjuvant chemotherapy (NAC) has been increasingly used in patients to reduce large tumors to a size eligible for breast-conserving therapy (BCT). However, the association between NAC and Ki-67 has not yet been fully elucidated. The aim of this study was to evaluate the prognostic significance of Ki-67, specifically after NAC followed by BCT, particularly in terms of locoregional recurrence (LRR).MethodsA total 217 patients who received BCT after NAC were retrospectively analyzed. In these patients, immunohistochemistry analyses defined four tumor subtypes, Luminal A, Luminal B, Triple negative, and HER2 type. Ki-67 was examined by immunohistochemistry in both pretreatment core needle samples and post-treatment surgical excision specimens. High Ki-67 expression was defined as >20%. The prognostic factors LRR, locoregional relapse-free survival (LRRFS), and overall survival (OS) were analyzed.ResultsIn total, LRR developed in 14 patients, and the 5 year-LRRFS was 94.2%. Post-treatment high Ki-67 expression, triple negative, the presence of lymphovascular invasion, and histological grade 3 were significantly high in LRR for prognostic factors (P < 0.05). There were significant differences in Kaplan–Meier method for LRRFS curves according to these three factors for patients receiving BCT following NAC (P < 0.05). There was a significant difference in the 5 year-OS for patients with and without LRR (41.7% vs. 93.9%, P < 0.001).ConclusionPost-treatment high Ki-67 expression could be one of the important prognostic factors of LRR, and require careful follow-up on LRR at the time of surveillance.