The CDC compared data from the 2002, 2004, and 2006 Behavioral Risk Factor Surveillance System surveys, which looked at fecal occult blood testing (FOBT) and lower endoscopy testing use among US adults 50 and older. Lower endoscopy, which includes sigmoidoscopy and colonoscopy, and FOBT are some of the most common ways to detect colon cancer. (See "Can Colorectal Cancer Polyps Be Found Early?" for more information on these tests.)

CDC researchers found that in 2006, 61% of US adults aged 50 and older reported receiving an FOBT within the last year or lower endoscopy in the last 10 years, up from 57% in 2004 and 54% in 2002. Numbers were on the rise regardless of race, insurance status, or socioeconomic class. Adults over 65 reported higher testing rates than adults aged 50-64, an increase attributed largely to the fact that Medicare started covering colon cancer screening tests in 2001.

While the ranks of the tested may be increasing, about 40% still aren't acting according to American Cancer Society screening guidelines, which recommend several different testing options for all adults aged 50 and over. Further, researchers found that minorities, the poor, and those without health insurance were less likely to be tested compared to whites, privately insured patients, and those with higher annual household incomes.

"This report is very disappointing when you look at subgroups, such as those who are uninsured, or among minority populations like Native Americans and Alaskans, who have very high rates of colorectal cancer," says Durado Brooks, MD, ACS Director of Prostate and Colorectal Cancer. "Certain populations with the greatest risk of developing colorectal cancer aren't being screened, and that's a major area of concern."

CDC researchers cited several potential reasons for why numbers might be lagging among certain populations. They point to a lack of patient education and awareness about testing, failure of physicians to recommend screening, and lack of health insurance and access to care. The report offers still more evidence of the effect of insurance status on cancer-stage and care (see "Report Links Health Insurance Status With Cancer Care" and "Late-Stage Diagnosis More Likely Among Uninsured").

Colon cancer is the second leading cause of cancer-related death in the US among men and women combined. About 108,070 new cases of colon cancer (53,760 in men and 54,310 in women) and 40,740 new cases of rectal cancer (23,490 in men and 17,250 in women) will be diagnosed in 2008. If caught early (in stage I), the relative 5-year survival rate is higher than 90%, compared with only about 10% in people with advanced disease. Screening is the most important tool for catching colorectal cancer early.

"These findings are an important reminder during National Colorectal Cancer Awareness Month that increasing colorectal cancer screening rates in adults and improving access to these tests for all Americans who need them, particularly among those groups who have lower screening rates, is an urgent national priority," said Robert A. Smith, PhD, ACS director of cancer screening, when the report was released.

The CDC's findings were published in the March 14, 2008 edition of the Morbidity and Mortality Weekly Report.