An association exists but causality has not yet been proved Incretin based treatment for type 2 diabetes improves hyperglycaemia without causing weight gain and is increasingly being used worldwide. Concerns have been raised about long term safety, as reported by Cohen,1 especially the risk of pancreatitis and pancreatic cancers—both adenocarcinoma and neuroendocrine tumours. Although concerns about adverse effects of incretin on the pancreas initially focused on acute pancreatitis, recent observational studies suggest an increased risk of subclinical pancreatic inflammation and pancreatic cancer.2 3 One study reported that pancreatic cancer was more common in patients with diabetes who used exenatide or sitagliptin than those who used other antihyperglycaemics.2 Similar concerns were raised by the drug commission of the German Medical Association in patients receiving exenatide.3 These concerns were reinforced by data from the Food and Drug Administration adverse event reporting system, which suggested an increased risk of pancreatic cancer in patients treated with incretins.4 Although cause for concern, these observational studies do not prove causality. Several epidemiological and mechanistic questions need to be considered when interpreting these …