No association between colon cancer and adenocarcinoma of the oesophagus in a population based cohort study in Sweden

Background-Previous reports have indicated an association between Barrett's metaplasia or adenocarcinoma of the oesophagus and colonic neoplasia, but the findings have been inconsistent. If true, such an association suggests common causal mechanisms. Aims-To test the hypothesis of an association between Barrett's metaplasia or adenocarcinoma of the oesophagus and colonic neoplasia. Methods-A population based, retrospective cohort study was performed on all Swedish patients with colon cancer diagnosed between 1958 and 1992. 538 500 person years at risk were reviewed among the 118 030 patients in the cohort (average follow up 4.6 years, median 2.1 years). The standardised incidence ratio (SIR), the ratio of the observed to the expected number of incident oesophageal adenocarcinomas, was used as a measure of relative risk. The expected number was derived from the entire Swedish population. Results-Eleven oesophageal adenocarcinomas were found during follow up in the cohort, as against 9.5 expected (SIR=1.2; 95% confidence interval 0.6-2.1). Analysis by latency intervals after diagnosis of colon cancer showed no trend towards increasing or decreasing risk over time. There were no important sex differences in relative risk. Conclusions-Results provide no support for a common link between colon cancer and oesophageal adenocarcinoma. Although the direct relation between colon cancer and Barrett's oesophagus was not looked at, a search for common aetiological factors or genetic defects may not be fruitful. Screening for colonic neoplasia among patients with malignant or premalignant oesophageal mucosa, or vice versa, may not be warranted.