Epidemiology and prognosis of synchronous colorectal cancers

BACKGROUND: The aim of this population-based study was to report on the incidence, treatment and prognosis of synchronous colorectal carcinomas. METHODS: Data were obtained from the population-based cancer registry of Burgundy. RESULTS: Between 1976 and 2004, 15 562 colorectal cancers were diagnosed. Some 3.8 per cent of patients had synchronous colorectal cancers. The risk of having synchronous cancers was higher in men (odds ratio (OR) 1.41 (95 per cent confidence interval (c.i.) 1.19 to 1.68)), when associated adenomas were present (OR 2.02 (95 per cent c.i. 1.69 to 2.41)), when there were adenomatous remnants on pathological examination (OR 2.10 (95 per cent c.i. 1.73 to 2.55)) and in patients aged over 75 years (OR 1.31 (95 per cent c.i. 1.08 to 1.59)). Synchronous tumours were more often located on the same intestinal segment, although the correlation was weak (kappa = 0.26). Resection for cure was performed in 74.8 per cent of synchronous cancers and 72.0 per cent of single cancers (P = 0.131). Five-year relative survival for synchronous (48.7 per cent) and single (48.3 per cent) cancers was almost identical. Stage, age, associated adenomas and adenomatous remnants were independent prognostic factors. CONCLUSION: Synchronous colorectal cancers convey a similar prognosis to single tumours. Men and patients aged over 65 years with associated adenomas are more prone to multiple colorectal cancers.