CT Colongraphy as a Tool for Colorectal Cancer Screening in African American Patients

Abstract

Purpose: Racial disparities in the presentation of colorectal cancer (CRC) have been well documented. African Americans (AA) have a higher incidence of CRC, are diagnosed at a later stage, and have a decreased survival when compared to Caucasians. One suggested reason for these differences is decreased utilization of the diagnostic modalities currently available. Computed Tomographic Colonography (CTC) has been suggested as a potential non-invasive tool for CRC screening. To date no studies have examined the utility of CTC in average risk CRC screening in AA patients. We aimed to examine the utility of CTC for average risk CRC screening in AA patients as well as rates of follow-up colonoscopy, after an abnormal exam. Methods: Data from 229 consecutive AA patients presenting from February 2007 until August 2012 for average risk CRC screening with CTC at a large city hospital, in Brooklyn, NY, was collected in a prospective study design. The data was analyzed for reason for referral, polyp detection rate (PDR), follow-up colonoscopy, and pathology. In addition to the overall PDR, particular rates for segments of the colon not previously visualized during prior incomplete colonoscopies were calculated to account for possible decreased PDR due to prior polypectomies. Results: The most common reason for referral for CTC was incomplete colonoscopy. The overall PDR for all patients was 8.7%. However, the verified adenoma detection rate, determined by subsequent colonoscopy with biopsy or polypectomy was much lower at 2.2%, as many of the patients failed to follow up with further workup (45% of those with polyps), or follow-up endoscopy failed to detect adenomas (30%). Median time to follow-up colonoscopy was 188 days. By segment of previously unvisualized colon, there were 169 segments of ascending colon/cecum in which 5 polyps (3.0%) were noted, 115 segments of transverse colon in which no polyps were noted, 89 segments of descending colon in which 1 polyp (1.1%) was noted, 74 segments of sigmoid colon in which 2 polyps (2.7%) were noted, and 66 segments of rectum in which no polyps were noted. None of these polyps have yet been confirmed as adenomatous. In the 171 incomplete colonoscopies that were followed by CTC, 7 polyps were visualized on CTC after not being seen on colonoscopy, however, only 2 of them have been confirmed to be adenomatous. Conclusion: While CTC would seem to be an attractive potential CRC screening modality in AA patients, low rates of adenoma detection, and suboptimal follow-up seem to limit its utility. While the reasons for low PDR are not clear, polyp location and morphology in this subset of patients may partially account for these findings.