Tumor cells mitotic activity marker Ki-67 in assessing the neoadjuvant chemoradiotherapy effectiveness in patients with rectal cancer
The aim of the study was to determine the expression patterns of protein Ki-67 in colorectal cancer tissue depending on the pathological characteristics of the tumor and to establish the possible relationship between marker level and the results of neoadjuvant chemoradiotherapy (NCRT). Ki-67 expression indexes were determined by immunohistochemistry in the biopsy and surgical material in 18 patients with adenocarcinoma of the rectum stage I-III before and after NCRT. It was found that the pre- treatment level of Ki-67 in cases of poorly differentiated tumors was significantly higher than that of highly differentiated, accounting for respectively 52,65±4,48 conv. units and 38,01±2,94 conv. units (p<0.001). Under the influence of NCRT the level of Ki-67 expression in the intact intestine decreased slightly. Expression of Ki-67 dramatically reduced to 32,45±1,19 conv. units (p<0.001) in the loci of residual tumor parenchyma compared with those before treatment (average level 46,08±3,14 conv. units) and inversely correlated with the degree of therapeutic pathomorphosis. Thus, a negative correlation between the expression of Ki-67 after NCRT and the level of the response to the applied treatment suggests the feasibility of using the Ki-67 definition to monitor the effectiveness of NCRT during combined and complex treatment of patients with rectal cancer. High expression of Ki-67 in the tumor before treatment, being characteristic of poorly differentiated tumors, corresponds to the high level of the malignant potential of the tumor.