Hereditary Colorectal Cancer Syndromes and Inflammatory Bowel Diseases: an ECCO CONFER Multicentre Case Series.

BACKGROUND: Hereditary colorectal cancer syndromes [HCCS] are rare polyposis or nonpolyposis syndromes with a higher risk of developing colorectal cancer [CRC]. Coexisting inflammatory bowel disease [IBD], including ulcerative colitis [UC] and Crohn's disease [CD], with HCCS is exceedingly rare and presumably increases the risk of early-onset CRC. METHODS: This was a multicentre case series performed as a part of the European Crohn's and Colitis Organisation [ECCO] Collaborative Network of Exceptionally Rare case reports [CONFER] project. RESULTS: This report includes 26 patients with IBD (10 UC, 15 CD, and one with IBD unclassified [IBD-U]) and concomitant HCCS. Among these 26 patients([median age 33 years, interquartile range [IQR] 20-44], 15 [57.7%] were males, 24 [92.3%] Caucasians, and two [7.7%] of Arab origin. HCCS was diagnosed before the IBD diagnosis in 11 patients [42.3%], after diagnosis of IBD in 11 patients [42.3%], and concurrently in four patients [15.4%]. Sixteen patients had Lynch syndrome, seven had familial adenomatous polyposis [FAP], two had MYH-associated polyposis [MAP], and one had attenuated FAP [AFAP]. The most frequent genetic mutations were those of APC [n = 7] and MLH1 [n = 7]. Overall, CRC developed in 38.5% of patients [n = 10]: in four patients [40%] after IBD diagnosis, in four [40%] patients before IBD diagnosis, and in two patients the two conditions were diagnosed simultaneously. Eighteen [69.2%] patients underwent colectomy or abdominal surgery: nine patients due to CRC diagnosis, five patients preventively due to the underlying HCCS, three due to the underlying HCCS and concomitant active IBD disease, and one patient because of active IBD disease. One patient died due to CRC. CONCLUSIONS: To date, this is the largest case series of patients with IBD and HCCS. The most frequent diagnosis of HCCS associated with IBD was Lynch syndrome. These data demonstrate the high malignancy rate and surgical intervention rate in this IBD cohort, despite the endoscopic surveillance. The optimal medical approach still needs to be addressed.