Although colorectal cancer screening tests reduce colorectal cancer mortality, only about half of U.S. men and women 50 and older receive the recommended tests, according to a report in the Cancer Epidemiology, Biomarkers and Prevention (cebp.aacrjournals.org), a journal of the American Association for Cancer Research.

The Centers for Disease Control and Prevention did a national health interview survey that found that percentage. Still, 50 percent is an improvement over 43 percent in 2000.

"Colorectal cancer is one of the leading cancer killers in the United States, behind only lung cancer. Screening has been shown to significantly reduce mortality from colorectal cancer, but a lot of people are still not getting screened," said Jean A. Shapiro, Ph.D., an epidemiologist at the CDC.

He said insurance coverage appears to be a major problem. Screening for those without health insurance was 24.1 percent compared to more than half of insured Americans. Among patients without a usual source of health care, the screening rate was 24.7 percent compared to 51.9 percent of patients with a usual source of health care.

Shapiro said increasing coverage would improve screening rates. He said screening rates likely improved because of increased media attention and the fact that Medicare began to cover it for a wider range of patients.

Other factors that influences screening were education (37 percent with less than high school diploma compared to 60.7 percent college grads), income (37.4 percent of those earning below $20,000 a year vs. 58.5 percent of people earning $75,000 or more) and contact with a physician.