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Re: 5-Aminosalicylate use and colorectal cancer risk in inflammatory bowel disease

Dear Editor,

We read this article with great interest. Thanks to author for submitting an interesting article. If the patients were on prednisolone or other immunosuppressive drugs then possible effects on CRC risk may be influenced by use of glucocorticoids or immunosuppressant. Question is which drugs really reduce the risk of colorectal cancer risk? As any effect of 5-ASA therapy on the risk of CRC could be mediated by the reduction in mucosal inflammation. If the patients were on multiple drugs, than evaluation of 5-ASA effects on IBD patients comparing those with non- IBD person taking 5-ASA is questionable! Was 5-ASA use for IBD was compared to controlled or quiescent IBD?

In this study IBD reference group was selected consisting of patients without a history of IBD or prescription for 5-ASA. If this group of patients were taking any other NSAIDs or any other drugs, what is the chance that those drugs may influence the results?

Here the author mentioned that two 5-ASA groups was matched to a reference patient by age (within five years), sex, and medical practice. They were also matched by calendar time (that is, they had to be registered at the practice at the date of the first record of a 5-ASA prescription of their matched patient). In the event of no eligible control patient within five years of age, an age and sex matched control patient was selected from another practice. Our question is if patients were selected from another practice suddenly there is chance of selection biases. So these patients were under threats to various biases.

Positive family history of colon/rectum polyps can be a cause of colorectal cancer development. How was the group of patients evaluated while calculating the risk of CRC development association with 5-ASA?

Environmental factor plays an important role in IBD; smoking is one of the important factors. Our question is was smoking countered as an important factor causing IBD and colorectal cancer. Number of patients who were smoking was not clearly identified in this study. Only smoking is enough to cause colorectal cancer.

In a recent article [2] we found that there are genetic materials involved in inflammatory bowel disease. Mutations in the nod2 gene are present in as many as one third of individuals with Crohn disease. We would aspect that spectrum of genes causing inflammatory bowel disease will be identified, attention will be focused on the mechanisms through which they lead to ulcerative colitis and Crohn's disease.

References

1. T P van Staa, T Card, R F Logan, and H G M Leufkens 5-Aminosalicylate use and colorectal cancer risk in inflammatory bowel disease: a large epidemiological study Gut, Nov 2005; 54: 1573 - 1578.