Just half of Americans who should be screened for colorectal cancer are actually getting tested, and lack of health insurance appears to be a major reason why, new research suggests.

“Colorectal cancer is the second leading cancer killer in the US, but it doesn’t have to be,” Dr. Jean Shapiro, an epidemiologist at the Centers for Disease Control and Prevention (CDC) in Atlanta and the study’s lead researcher, told Reuters Health. She pointed out that screening can not only identify cancer early, but may also spot precancerous polyps that can be removed before cancer develops.

Regular screening for colorectal cancer is recommended for people 50 and older, but screening rates are known to be low, Shapiro and her colleagues note in the journal Cancer Epidemiology, Biomarkers and Prevention. To investigate reasons why people might not be getting screened, the researchers analyzed data on 13,269 people aged 50 and older who participated in the 2005 National Health Interview Survey.

Exactly half of the survey respondents said they had been screened for colorectal cancer with a fecal occult blood test (FOBT) in the past year, endoscopy within the past 10 years, or both. But just 24.1 percent of people who had no health insurance had gotten tested. Among people who reported having no usual source of health care, 24.7 percent had been screened.

Shapiro and her team also saw sharp differences in colorectal cancer screening rates based on education and income. Thirty-seven percent of people who hadn’t finished high school had been screened, while 60.7 percent of college graduates had.

Among people with household incomes of $20,000 or less, 37.4 percent had been screened, compared to 58.5 percent of those with incomes of $75,000 or more. Just 19.5 percent of people who hadn’t seen a doctor in the past year had been screened.

Roughly 50 percent of survey respondents who failed to get screened said they had “never thought about it,” while about 20 percent said their doctor “did not order it.”

The findings make it clear that more people need to be informed about colorectal cancer screening, that doctors must do a better job of telling their patients about the test, and that more people should have health insurance coverage in the US, Shapiro said.

Current guidelines from the US Preventive Services Task force recommend people 50 and older get an FOBT every year, flexible sigmoidoscopy every five years, colonoscopy every 10 years, or a double-contrast barium enema every five years, the researchers note.

“People should talk to their doctor about what the best way for them to be screened is,” Shapiro said. Health insurance will usually cover colorectal cancer screening, as will Medicare, she added.

Individuals without health coverage can call 1 (800) 4-CANCER or 1 (800) ACS-2345 to find out about low-cost screening options in their community, or check with their local department of health. More information on colorectal cancer screening is available at the CDC’s Web site at http://www.cdc.gov/screenforlife.

SOURCE: Cancer Epidemiology, Biomarkers and Prevention, July 2008.