Distribution of colorectal cancer in young African Americans: implications for the choice of screening test

Background We recently reported on a left-sided predominance of colorectal cancers in the young (under age 50). Given the predilection of young African Americans for the disease, we wondered if there may be a difference in the biology of colorectal carcinogenesis between this group and Caucasians. Objective Compare the distribution of colorectal cancer in African American patients and Caucasians under age 50, and describe implications for screening in these groups. Patients Colorectal cancer patients diagnosed under the age of 50 between the years 2000 and 2016. All races other than African American and Caucasian and all patients with hereditary colon cancer or inflammatory bowel disease were excluded. Outcome measures: race, age at diagnosis (5 subgroups: <20, 20-29, 30-39, 40-44, and 45-49 years) and cancer location; right (cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure), left (descending colon and sigmoid colon), or rectal. Results 759 patients were included; 695 (91.6%) were Caucasian and 64 (8.4%) were African American. Most cases were diagnosed between ages 40 and 49 (African American=75%, Caucasian=69.5%). Rectal cancer was most common in both races, although significantly more common in Caucasian than in African American patients (64.2% vs 39.1%). Right colon cancer was more commonly found in African Americans (37.5%) compared with Caucasians (18%) (p=0.0002). The ratio of rectal to right-sided colon cancer in African Americans was 1:1 compared with 3.6:1 in Caucasians. Limitations Relatively low number of African American patients Conclusion The high rate of right-sided cancer in young African American patients means that they should be screened with colonoscopy. The increased incidence of right-sided cancers may represent a different biology of carcinogenesis in African Americans and deserves further study.