Incidence of cancer for patients after bariatric surgery: evidence from 33 cohort studies

Background With the rising prevalence of severe obesity, bariatric surgery has emerged as a crucial treatment option. As the number of surgeries performed worldwide increases, there has been growing interest in the impact of bariatric surgery on cancer incidence. While several studies have examined this relationship, the topic remains controversial. Objectives We conducted this systematic review of cohort studies with meta-analysis to evaluate the effect of bariatric surgery versus nonsurgical treatment on overall cancer incidence. However, the effects may vary when focusing on specific cancer types, surgical procedures, or gender, so we conducted additional subgroup analyses. Setting A meta-analysis. University hospital. Methods The Cochrane, Embase, PubMed and Web of Science databases were searched for studies from 1 January 2000 to 1 December 2022. Meta-analysis was conducted to evaluate the pooled effect and further implemented subgroup analysis stratified by cancer type, operation type and sex. Results All cohort studies were included in this meta-analysis from 18216 studies. The overall cancer incidence demonstrated a significant decrease in the group with bariatric surgery (OR = 0.56, P = 0.000, 95% CI 0.46 to 0.68). In subgroup analysis, similar decrease effect was found in nine cancers. Furthermore, the incidence of cancer decreased significantly in male (OR = 0.66, P = 0.001, 95% CI 0.51 to 0.85) and female (OR = 0.63, P = 0.000, 95% CI 0.57 to 0.69) patients and patients undergoing gastric bypass (OR = 0.46, P = 0.000, 95% CI 0.33 to 0.63) or sleeve gastrectomy (OR = 0.44, P = 0.001, 95% CI 0.27 to 0.70). Conclusions In the overall analysis, bariatric surgery could reduce the incidence of cancer significantly. Further large-scale well-matched studies are needed to verify the protective effect of bariatric surgery on cancer incidence.