The Role of Ki-67 in HR+/HER2- Breast Cancer: a Real-world Study of 956 Patients

Abstract

Purpose: This retrospective study aimed to determine the most suitable cut-off value of Ki-67 expression and further explore the prognostic effect of Ki-67 in hormone receptor positive and human epidermal growth factor receptor 2 negative (HR+/HER2-) breast cancer;Methods: We assessed the Ki-67 expression of 956 patients with HR+/HER2 breast cancer diagnosed in General Hospital of Ningxia Medical University from 2015 to 2019 by immunohistochemistry, The disease-free survival (DFS) was defined as the time from postoperative to the first local recurrence, distant metastasis or death of the disease. Results: 22.5% was used as the cut-off for low/high Ki-67 expression in HR+/HER2- breast cancer; compared with the commonly used threshold value of Ki-67(14%) in clinic at present, the consistency of the two value is moderate (Kappa = 0.484, P<0.001). The expression of Ki-67 was increased with the increase of grade. (Median: G1:10%; G2:20%; G3:40%. Mean: G1:13%; G2:23%; G3:39%, P<0.001). During the follow-up that 61 patients developed recurrence or metastasis which Ki-67 low expression was found in 21 cases and high expression in 40 cases, the patients with Ki-67 ≥ 22.5% had a 2.937 higher risk of early recurrence and metastasis than the patients with Ki-67< 22.5%, the DFS in patients with high Ki-67 expression was lower than the patients with low Ki-67 expression (96% VS 89%, P<0.05). The common position of distant metastasis were bone, liver and lung, and rare metastases were adrenal gland, bone marrow and pericardium. Recurrence and metastasis mostly occurred in the second and third year after operation, and multi-site metastasis was more common.Conclusions: The cut-off value of Ki-67 expression in HR+/HER2- breast cancer is 22.5%; The patients with Ki-67 ≥ 22.5% had a 2.937 higher risk of early recurrence and metastasis than the patients with Ki-67 < 22.5%.