[Obesity from the Perspective of Surgical Oncology]

Up to 40% of all adults worldwide are overweight or obese. Besides the established obesity-related comorbidities, such as type 2 diabetes mellitus, hypertension or NAFLD (non-alcoholic fatty liver disease), the focus of interest is shifting towards the influence of increased body weight as a risk factor for the development of malignant diseases. For more than 20 different types of malignancies, interactions between increased body weight and cancer risk have been established. Pathophysiological influences of obesity on carcinogenesis are diverse, including factors such as chronic inflammation, hyperinsulinaemia and insulin resistance, various changes in growth factor and changes in sex hormones. In cohorts of visceral oncology patients, malignancies such as colorectal carcinomas, hepatocellular carcinomas, adenocarcinomas of the pancreas, oesophageal and gastric carcinomas are also linked to an increased disease risk with increasing body weight. Since obesity must be considered a preventable or at least treatable cause of cancer, this review examines the influence of obesity in the field of visceral oncology, examining the effects of obesity on tumour prevalence, prevention and diagnostic testing, as well as its influence on treatment and prognosis. Furthermore, this review explores the current evidence on the influence of bariatric surgery on the prevalence of these obesity associated tumours. For example, in the case of colorectal carcinomas, the evidence base following bariatric surgery is mixed, painting an inhomogeneous picture. On the other hand, significantly lower prevalence of pancreatic adenocarcinoma and hepatocellular carcinomas is to be noted. The latter effect can be explained by the decrease in non-alcoholic fatty liver disease (NAFLD) associated with weight loss. Despite the justified concern that bariatric procedures (especially gastric sleeve resection) lead to increased prevalence of malignancies of the oesophageal junction, the currently available epidemiological data does not seem to identify a relevant increase in the incidence of these malignancies.