AB0 BLOOD TYPES AND MALIGNANT COLORECTAL NEOPLASMS OF DIFFERENT LOCATION: A RETROSPECTIVE ANALYSIS OF 1570 CASES

Background: AB0 blood type antigens are unequally expressed in different portions of the colon resulting in so-called proximal-distal gradient. In most research studies considering the link between blood types and colorectal cancer, this gradient has not been taken into account. In the present context the findings of such studies are not convincing, no evidence-based results are reflected in literature. Valid studies of this association require antigenic distribution of the colon and malignant tumor location to be taken into account. Aim : To assess the possible relation between AB0 blood type antigens and malignant tumors located in different parts of the large intestine. Materials and methods: We performed a case-control study with retrospective analysis of medical records on patients with the presented disease (cases) and patients who did not suffer from it (controls). Required data was obtained from regional oncological centers of South Kazakhstan, Karaganda, East Kazakhstan, and Mangystau regions. Every third case of colorectal cancer registered in 2011−2016 years was included in the survey. The studied association was estimated by means of a chi-square test. A multinomial logistic regression was used to calculate the odds ratio (OR) with confounding risk factors to be taken into account. Shares of the samples were compared by means of Student’s t-test. A critical level of statistical significance (p-value) was considered to be 0.05. Results: Each group included 1570 patients. Gender, age, and ethnic distribution did not differ statistically in cases and controls (p>0.4 for all comparisons). When blood type distributions were compared between groups regardless of tumor locations, any significant difference was not revealed (p=0.141). When similar calculations were applied to specific parts of the large intestine, the association between 0 blood type and malignancies of distal portions of the colon was demonstrated (p=0.0002). When we calculate the odds ratio for the disease development in the colon parts (using a multinomial logistic regression), the following results were obtained: 1.518 (p=0.004) for 0, 0.781 (p=0.099) for A, 0.785 (p=0.143) for B, and 0.965 (p=0.884) for AB blood types. Conclusions: The results of the present study revealed a statistical correlation between the 0 blood type and malignant tumors located in the distal portions of the colon.