About 17 percent of colorectal cancer cases among elderly Americans could be prevented if they underwent a relatively simple screening test every year, a congressional report says.

The Office of Technology Assessment estimated Sunday that an annual test for hidden blood in the stool would prevent about 23,000 cases of colorectal cancer in the 2.1 million people who are 65 or older.Each year, about 110,000 people age 65 or older are diagnosed with colorectal cancer. As people age, their risk of such cancer increases.

The screening procedure, called a fecal occult blood test, reduces cancer cases by allowing doctors to detect polyps in the colon before the flaplike growths turn cancerous. Such tests also cut down on deaths by catching colon cancer in its earlier, treatable stages.