La chirurgie bariatrique permet-elle une diminution du risque oncologique chez le sujet obèse ?

Abstract

It is now recognized firtsly that obesity is a risk factor for cancer, and secondly that bariatric surgery can decrease the overall morbidity and mortality of the obese subjects. But does bariatric surgery allow a reduction of oncological risk in obese subjects? Recently, Tee et al have published a meta -analysis on the major controlled studies on this subject. The relative risk (RR) of cancer in operated obese subjects compared to not operated obese subjects was 0.55 (CI95 [0.41 to 0.73], p <0.0001). RR was 0.68 (CI95 [0.41 to 0.73], p <0.001) in women and there was no demonstrated protective effect in men (RR = 0.99, CI95 [0.74–1.32]). The incidence of obesity-related cancers (oesophagus, colon — rectum, pancreas, breast, endometrium, kidney, non-Hodgkin lymphoma, leukaemia, multiple myeloma, liver and gallbladder) would be particularly affected by the positive effect of bariatric surgery with a hazard ratio of 0.62 (CI95 [0.49 to 0.78], p <0.0001) according to the study by Adams. The beneficial effect of bariatric surgery on nonalcoholic liver steatosis would allow in theory a decrease in hepatocarcinoma risk. It would be the same for gastrooesophageal reflux (treated with gastric bypass) for oesophagus adenocarcinoma. However it seems that the low incidence of these cancers associated with low power of studies did not highlight the decrease of incidence. Mechanistic explanations point the role of inflammatory cytokines and certain hormones such as estradiol, insulin, increased in obese subjects and involved in tumorigenesis, and that would decrease after bariatric surgery. Adiponectin, increased after bariatric surgery, would also be protective against the cancer. Thus, bariatric surgery, which is now the most effective treatment for sustained weight loss seems, with a high level of evidence, to reduce the incidence of certain cancers.