The rate of new colorectal cancer cases in the U.S. dropped to 45.4 per 100,000 people in 2007 from 52.3 per 100,000 people in 2003, representing nearly 66,000 fewer cancers, according to a study by the Centers for Disease Control and Prevention (CDC).
There were 32,000 fewer deaths from the disease during that time, the report said.
About half the decline in the number of cases and deaths was due to increased screening, CDC Director Thomas R. Frieden told reporters in a telephone conference call on Tuesday.
"One thing we know is that screening works," Frieden said.
Colon cancer remains the nation's second most deadly cancer, killing more than 53,000 people per year, the CDC said. Only lung cancer is deadlier.
Screening for colorectal cancer, which is recommended for men and women beginning at age 50, has increased to 65% in 2010 from 52% in 2002, the CDC report said.
But about a third of those between the ages of 50 and 75 -- or 22 million people -- are not up to date with their screenings, the CDC said.
Screening is designed to detect precancerous polyps that can be removed before they turn into cancer. Frieden told reporters that he recently had four noncancerous polyps removed after testing.
"Colon cancer is largely preventable," he said. "If you find it early enough, you can prevent cancer."
Frieden expressed concern that screening, after steadily increasing in recent years, may be leveling off. He said the largest single reason patients do not get screened is that their doctors do not suggest it.
Death rates from colorectal cancer decreased in 49 states and Washington, DC, with the largest declines in states with the most screening, the CDC said. Only Mississippi had no change in its death rate.
In 2007, Washington, DC, reported the highest number of colorectal cancer deaths per 100,000 people, and Montana and Colorado reported the lowest.
North Dakota had the highest number of cases per 100,000 people, and Utah had the lowest.
(Editing by Colleen Jenkins and Greg McCune)