['Considering the low incidence of colon cancer after an initial episode of colonic diverticulitis in some categories of patients, some authors suggested to exempt them from colonoscopy. However, this incidence has never been compared to that of a reference population, and predictors of cancer are still poorly investigated. We aimed to determine the 1-year incidence of colon cancer at the site of diverticulitis in patients diagnosed with left colonic or sigmoid acute diverticulitis, to compare this incidence to a reference population to state whether endoscopy is required or not, and to identify predicting factors of cancer to better target subpopulations needing that examination.', 'All patients admitted at the University Hospitals of Geneva for left colonic or sigmoid acute diverticulitis were included. Patients with a previous history of colon cancer or non-available for follow-up were excluded. Demographic data, haemoglobin values, and the Hinchey score were documented. This cohort was matched with the Geneva Cancer Registry to look for cancer occurrence at the site of diverticulitis within 1\xa0year. Predictors of cancer were assessed using univariate logistic regression and the risk of cancer by comparing observed cases to a reference population using standardized incidence ratios.', 'The final cohort included 506 patients. Eleven (2.2\xa0%) had a diagnosis of cancer at the site of diverticulitis within 1\xa0year. The mean age was significantly different between patients with cancer and others. No predictor of cancer could be identified, except a trend for an increased risk with advancing age (p\xa0=\xa00.067). The standardized incidence ratios showed a 44-fold increased risk of cancer among the cohort compared to the reference population.'] Is the incidence of colon cancer among patients diagnosed with left colonic or sigmoid acute diverticulitis higher than in the general population?