ABO blood classification and the risk of lung cancer: A meta-analysis and trial sequential analysis.

Patients with certain ABO classifications are at increased risk of certain types of malignancies. In the present study, a meta-analysis was performed to explore the association between the ABO blood group and the risk of lung cancer from an evidence-based medical perspective. The PubMed, Embase, Web of Science, Medline, China National Knowledge Infrastructure, Google Scholar, Science Direct and Wanfang databases were searched for relevant papers. Review Manger 5.4 was used to analyze the association between the ABO blood group and the risk of lung cancer. Trial Sequential Analysis (TSA) was used to determine whether the sample size of the meta-analysis was sufficient. A total of 29 studies were included in this paper. The results of the case-controlled studies showed that the proportion of patients with blood type A in patients with lung cancer was significantly higher than that in healthy individuals [odds ratio (OR), 1.10; 95% confidence interval (CI), 1.02-1.19]. Based on the subgroup analysis, type A blood showed heterogeneity in ethnicity and source of control (social or hospital). Additionally, type O blood was determined to be a protective factor for lung cancer in Caucasians (OR, 0.92; 95% CI, 0.85-0.99). TSA results suggested that there were sufficient participants in the case-controlled studies. Overall, the results of the cohort studies showed that the risk of lung cancer and blood type were weakly associated, and that the difference was not statistically significant. The case-controlled studies suggested that blood type A was associated with a higher risk of lung cancer. In addition, the analysis confirmed that Caucasians with type O blood had a lower risk of lung cancer. However, prospective cohort studies have not been able to draw this conclusion. Different experimental designs may have had a notable influence on the results obtained.