The Author Replies
Epidemiological studies have typically shown that individuals with Crohn’s disease of the large intestine are at increased risk for colorectal cancer.7 The exact magnitude of the threat is uncertain, but recognized risk factors include age at disease onset, extent/duration/severity of disease, inflammatory complications, and presence of primary sclerosing cholangitis. It is hypothesized that host inflammatory and immune responses critically contribute to the pathogenesis of colorectal cancer in these patients. Unlike sporadic colorectal cancer that likely originates from unifocal dysplasia, colitis-associated cancer probably arises when inflamed colonic mucosa undergoes a field change of cancer-associated molecular modifications that lead to multiple foci of dysplasia.8
In patients with Crohn’s disease of the large bowel undergoing resection for high-grade dysplasia alone, Kiran and associates from the Cleveland Clinic reported that 10 of 22 patients (45%) were found to harbor invasive cancer plus dysplasia in the resected specimen.9 Moreover, one of the 11 patients in whom the large bowel was left at the time of resection for high-grade dysplasia developed cancer in the retained segment after an average follow-up of approximately 5 years. A separate study from the same institution investigated patients undergoing colorectal cancer resection on a background of Crohn’s disease.10 They reported that 2 of 14 patients (14%) developed metachronous cancer in the remaining large bowel 3 and 4 years after undergoing curative resection. In both studies, the average patient age at the time of initial resection was over 50 years.
A similar study by Maser and colleagues from The Mount Sinai Hospital, reported on a series of patients managed between 2001 and 2011.11 They found new high-grade dysplasia in the retained large bowel of 2 of 4 patients 0.7 and 6.1 years following segmental colectomy or less than total proctocolectomy for Crohn’s disease complicated by high-grade dysplasia. More worrisome is that another 64 patients were left with large bowel following resection for cancer in the same setting, and 25 of these patients were found to have a metachronous cancer after an average follow-up period of only 6.8 years. Although 80% of patients manifested inflammation at the site of their original cancer, the metachronous cancer was associated with inflamed large bowel in only 52% of cases.
The recommended approaches to detection and management of colorectal dysplasia complicating Crohn’s disease have changed over the past 2 years with publication of the SCENIC international consensus statement.12 Although these guidelines are not universally embraced in the United States, they have been adopted by many major centers in Europe and North America. The consensus statement endorses surveillance by using dye-based high-definition chromoendoscopy with targeted biopsies and suggests that operative resection is limited to those individuals with dysplastic areas that cannot be completely resected by an experienced endoscopist using chromoendoscopy and endoscopic techniques.