WASHINGTON—Cancer in the proximal colon, the right part of the colon closest to the small intestine, has been increasing in African-American men since the mid-1990s.
The rising incidence stands in marked contrast to the overall decrease in colorectal cancer rates seen over the past 20 years, said Ananya Das, MD, associate professor, Division of Gastroenterology, at the Mayo Clinic in Scottsdale, Arizona. Dr. Das presented the findings at the Digestive Disease Week 2007 conference (abstract 431).
Dr. Das and his colleagues analyzed millions of records from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database, calculating sex-, race-, and site-specific incidence for all patients with confirmed, invasive, primary colorectal cancer between 1973 and 2003.
Overall colorectal cancer rates declined during this period in both blacks and whites and in both men and women, the researchers found. But when they looked at proximal colon cancer among African Americans, they "came up with a very startling observation," Dr. Das commented. Starting in the mid-1990s, rates began rising for African Americans, especially men.
Although the reason for the increase is unknown, it does suggest that screening among African Americans should include complete colonoscopies, Dr. Das said. Colonoscopy, in contrast to sigmoidoscopy, includes the proximal section of the colon.
"There are very convincing data that African Americans have lower rates of colonoscopy screening, even after having colon cancer," Dr. Das said. "That could help explain the findings."
Obesity as a risk factor
