Gall stones, colorectal and other cancers.

Commentary Gall stones, colorectal and other cancers Johansen and colleagues present the results of a cohort study with a substantial size and a non-differential follow up with regard to different cancer outcomes. However, this paper is, in essence, two different studies. One part constitutes an in depth study of the potential association between gall bladder disease and colorectal cancer and the other part constitutes a 'fishing expedition' with regards to other cancer sites without any a priori hypothesis. In this latter study, the authors found an association between gall bladder disease and cancer of the pancreas and small intestine as well as for breast cancer in women. The association between colorectal cancer and gall bladder disease has been the subject of a veritable abundance of studies, which, three years ago, were summed up in a meta-analysis' followed by a commentary by Dr Robert Sandler in which he stated that there are probably 'more fruitful fields for the understanding of colorectal cancer' and 'future researchers should provide the underlying reason why an additional study on this subject is needed'.2 However , this study includes at least two unique features. Firstly, in the analysis the authors were able to adjust for clinically defined obesity. Secondly, besides confirming previous results of, at most, a modest increased risk of cancer of the colon, the authors were also able to differentiate between patients with gall bladder disease subjected to cholecystec-tomy and those left with an intact gall bladder. The results show that the operation as such does not change the risk but, as the authors point out, the weak association is probably due to shared risk factors for the two diseases. There was also an increased risk for cancer of the small bowel confined to carcinoid tumours most prominent during the first five years of follow up. Because of the insidious symptoms of carcinoid tumors such a finding is not surprising as the symptoms from the tumour could be the underlying reason for the diagnosis of gall stones and a subsequent cholecystectomy. As the duration between symptoms and the final diagnosis of carcinoid can exceed five years,3 this could also explain the longterm increased risk evident in the results. A similar explanation for the first five years of follow up could also explain the findings of an increased risk for pancreatic cancer in the cohort. A recent Swedish cohort study showed similar results4 and findings …