Was ulcerative colitis one of the risk factors of colorectal cancer?

Abstract

We read the recent published paper in this journal of J Gastrointest Oncol by Zhang and colleagues entitled "Secondary colon cancer in patients with ulcerative colitis: a systematic review and meta-analysis" (1). They performed a systematic review and meta-analysis to assess the correlation between ulcerative colitis (UC) and colon cancer. We appreciate Zhang et al. (1) for the valuable study, however, after a careful learning of the literature, several limitations should be noticed.First, in the results section of the abstract, Zhang et al.(1) performed the meta-analysis by random-effect model because of statistical heterogeneity (Chi 2 =103.10; I 2 =90%; P<0.00001) and found that there were no significant differences between colon cancer in patients with UC and patients without colon carcinoma (Z =12.44; P<0.00001). However, we believe the interpretation of the results was false. There should be significant difference due to P<0.00001.Second, in the statistical methods section of this article, Zhang et al. (1) stated that the odds ratio (OR) was used as an effect size for dichotomous variables. Whereas, in this meta-analysis, the effect size actually was relative risk (RR) showed in figures 5,6 and the OR was not reported in the study. Therefore, we believe the irrelevant effect size depicted would lead to misunderstanding.

Meta-analysis and systematic review of the relationship between ulcerative colitis and colon cancer

“…We thank Guo et al for their comments on our published article “ Secondary colon cancer in patients with ulcerative colitis : a systematic review and meta - analysis ” ( 1 ).…”