RESUMEN
PURPOSE: Despite colonoscopic surveillance, Lynch syndrome patients develop colorectal cancer (CRC). Identification of modifiable factors has the potential to improve outcome of surveillance. The aims of this study were to determine (1) characteristics of patients with CRC, (2) endoscopic and histological features of these cancers, and (3) quality of the previous colonoscopy. METHODS: Approximately 2,200 medical reports from proven and obligate mutation carriers identified at the Dutch Lynch Syndrome Registry and two large hospitals were retrospectively analyzed for the presence of an interval cancer defined as CRC diagnosed within 24 months of previous colonoscopy. RESULTS: Thirty-one interval cancers were detected in 29 patients (median age of 52 [range 35-73]), after a median time of 17 months. All were MLH1 or MSH2 mutation carriers, and 39 % had a previous CRC. In patients without previous surgery for CRC, 84 % was proximally located. Of all interval cancers, 77 % were at local stage (T1-3N0Mx). In three patients (9 %) with an incomplete previous colonoscopy, CRC was located in the unexamined colon. In six of the nine patients with an adenoma during previous colonoscopy, the cancer was detected in the same colonic segment as the previously removed adenoma. CONCLUSIONS: Interval cancers were detected in MLH1 and MSH2 mutation carriers, especially in those with a history of previous CRC and between 40 and 60 years. Interval cancer could be related to incompleteness of previous endoscopy and possibly residual adenomatous tissue. Further reduction of the interval cancer risk may be achieved by optimizing endoscopy quality and individualization of surveillance guidelines.