Prognostic and Molecular Classification Value of Ki-67 Index in Patients With Breast Cancer

Background: The Ki-67, which is a proliferative index, became more important in making treatment decisions of breast cancers. But a few factors limited its use in clinical practices, especially the assessment of positive cells percentage of Ki-67 and the cut-off value of Ki-67. In this study, we examined the expression of Ki-67 by immunohistochemical method, and evaluated the value of Ki-67 index in patients with breast cancers systematically. Methods: : The expression of Ki-67 was detected by immunohistochemical method, the relationship between over-survive (OS), disease free survive (DFS) of patients with BCs and Ki-67 index，and the value of Ki-67 in molecular classification of BC were analyzed with SPSS ver. 18.0 and GraphPad Prism software. Results: : There were markedly difference between OS in patients with BC when the Ki-67 index arranged from 46% to 68% (χ2 = 6.87, P = 0.0088; χ2 = 7.69, P = 0.0056 respectively), and the same results were also found when the positive density was added to the Ki-67 index, but the positive density has limited value in assessment the value of Ki-67. There were markedly difference between DFS in BCs when the Ki-67 index arranged from 50% to 58% (χ2 = 7.31, P = 0.0068; χ2 = 7.88, P = 0.005). When using 14% as a cut-off point to classify the molecular type of BC, the Luminal A-type patients had statistical differences with patients with HER-2 over-expression, with triple negative type BC in term of OS respectively (χ2 = 4.8, P = 0.028; χ2 = 3.89, P = 0.049). There’s statistical difference between OS of patients with HER-2 over-expression BC when the Ki-67 index fell in the range of 49%- 60% (χ2 =4.97, P = 0.0259; χ2 =5.61, P = 0.0178, respectively). There were statistical differences between the Luminal A-type BC and HER-2 over-expression BC in term of OS (χ2 = 4.65, P = 0.031) according to suggestions of the CSCO consensus in 2019, there were statistical differences between two groups of Luminal B HER-2 (-) type BCs when the Ki-67 index was 52% (χ2=6.61, P = 0.0101). Conclusions: : Ki-67 index can be used to assess the OS and DFS of patients with BC, and the positive density of Ki-67 has little value in assessment of prognosis in patients with BC. Different molecular classification methods may influence the assessment of prognosis and the results of molecular type in patients with BC.