Ki-67 Index and Its Correlation with Clinical and Pathological Variables in Breast Cancer

The role of the Ki-67 index as a prognostic marker in breast cancer is controversial. This study was undertaken to assess the association of Ki-67 index with other clinicopathological factors in breast cancer. The prospectively conducted study included 127 female patients with clinical tumor stage 1-3 and nodal stage 0 or 1 treated between March 2015 and March 2017. Ki-67 index was correlated with age, tumor size, lymph node status, histological grade, ER, PR, HER2, and molecular subtypes using Chi-square or Fisher's exact test. Mean age of the patients was 53.28 years (range, 25-86 years). Mean Ki-67 index was 33.59 (range, 2.5-95). Ki-67 index showed a positive correlation with pathological stage (p=0.025), grade (p=0.0001), and molecular subtype (p=0.0001) of the tumor. It was inversely associated with ER (p=0.0001) and PR status (p=0.0001). Its association with pathological nodal status (p=0.06) and size (p=0.08) of the tumor was not statistically significant. There was no correlation with age (p=0.892) and HER2 status (p=0.287). Association of the Ki-67 index with common prognostic factors such as grade, stage, ER, PR, and molecular subtype suggests its role as a prognostic factor in breast cancer.