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Colorectal cancer after gastric surgery: a meta-analysis.

BACKGROUND
Until now, the question of whether previous gastric surgery results in an increased risk of colorectal cancer has remained controversial. A meta-analysis was performed to resolve this issue.


METHODS
The numbers of colorectal tumors in the two populations with and without gastric surgery were retrieved from all relevant articles found through a MEDLINE search. If available, the most detailed breakdown of the data by patient gender, type of peptic ulcer, type of surgery, time since gastric surgery, and by tumor location was chosen. The Mantel-Haenszel procedure was used to calculate a weighted odds ratio from the individual studies. The method of DerSimonian and Laird was used to calculate a weighted average of the difference between tumor rates in patients with and without gastric surgery.


RESULTS
The summary odds ratio was 1.09 with a 95% confidence interval of 0.96-1.24. The length of time after surgery, gender, tumor location, initial ulcer type, and different types of surgery were not associated with any significant influence. The summary rate difference was not significantly different from zero. The test for heterogeneity yielded a chi 2 = 26.87, df = 13, p = 0.013. After ignoring one obvious outlier study, the chi 2 test dropped to a nonsignificant level. A L'Abbé plot failed to show any prevailing influence of rate size on the overall heterogeneity among the various studies.


CONCLUSIONS
Surgery for peptic ulcer does not result in an increased risk for colorectal tumors. This lack of influence was shown consistently by all tests of the present meta-analysis.