Cancer incidence, type, and survival after bariatric surgery.

BACKGROUND

Many types of cancer have been found to be associated with being overweight or obese. Literature has demonstrated a reduction in cancer risk in patients who have undergone bariatric surgery.

OBJECTIVES

To compare the incidence and types of new cancer diagnoses, cumulative cancer incidence, cancer risk, and overall survival in patients with obesity who underwent bariatric surgery with that of those who did not.

SETTING

Community-based academic medical center.

METHODS

We retrospectively compared the rates and types of new incident cancers in a bariatric surgery cohort (Bariatric group) with those of a non-surgical cohort (Comparison group). The Comparison group was chosen from patients who had a clinic visit in our health system within 30 days of each bariatric surgical operation and matched on age, sex, and body mass index. Patients who had a cancer diagnosis prior to having bariatric surgery were excluded from the Bariatric group and patients who had a cancer diagnosis prior to the clinic visit on which they were matched were excluded from the Comparison group. Relative risk of cancer by type was calculated. Chi-square and Fisher exact tests were used for categorical data analysis, and Wilcoxon rank-sum for continuous data. The Kaplan Meier estimator with the log-rank test was used to compare overall survival between groups, while competing risks survival analysis with the Gray test for equality was used to compare cancer incidence in the Surgery group with that in the Comparison group.

RESULTS

After matching, the Bariatric group had 1593 patients and the Comparison group had 2156. The Bariatric and Comparison groups had 82 and 222 new incident cancer cases, respectively (P < .001). The 10-year incidence of any new cancer in the Bariatric group was 6.5%, compared with an incidence of 12.1% in the Comparison group (P < .001). Relative risk of cancer in the Bariatric group was lower than that of the Comparison group, with the greatest differences in endometrial (88.8%), kidney (77.4%), thyroid (72.9%), and ductal carcinoma in situ (71.2%) cancers. The 10-year overall survival rate was higher in the Bariatric group than in the Comparison group, 93.3% versus 80.6%, respectively (P < .001).

CONCLUSIONS

Bariatric surgery reduces the risk for developing cancer and offers survival advantage when compared with similar patients who do not undergo bariatric surgery.