Does Bariatric Surgery Lower the Risk for Incident Cancer?

Does weight-loss surgery have an impact on the incidence of cancer? In a recent retrospective follow-up study published in Annals of Surgery, the authors compared 22,198 patients who had undergone bariatric surgery with a carefully matched group of 66,427 control patients.^[1]

All patients were members of the Kaiser Permanente health plan where data could be extracted from electronic health records. Eighty-one percent of the patients were female. After a mean follow-up of 3.5 years, the overall risk for all cancer was 33% lower in operated compared with nonoperated patients. For the group of tumors known to be associated with obesity—postmenopausal breast, endometrium, colon, and pancreatic—the risk reduction was even greater, at 41% (P < .001).

A Gratifying Finding at Least in the Short Term

This large study provides additional evidence that bariatric surgery reduces the risk for cancer, at least in the first few years of follow-up. It's important to note that most of the patients in the study were females; thus the results were significant for lowering the risks for postmenopausal breast and endometrial cancers—two tumors strongly associated with obesity that occur only in females.

Gastric bypass and sleeve gastrectomy procedures were known to be performed in 88% of patients, so presumably the favorable results apply mainly to these two types of procedures.

The frequency of esophageal adenocarcinoma was markedly reduced in the follow-up period: no cases in the operated group versus 16 in the control group (P = .02). This gratifying finding may be related to a reduction in acid reflux following gastric bypass surgery—the commonest procedure in this study.

This study differs from other somewhat smaller reports in that there was no observed increased risk for colon cancer.^[2] One shortcoming of the report is that the mean follow-up was only 4 years. However, because the reduction in cancer incidence remained steady over this period it seems reasonable to anticipate that the lower cancer rates will persist over longer time.

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