"No one screening test is right for everyone," lead researcher Amy Knudsen, from the Institute for Technology Assessment at Massachusetts General Hospital in Boston, told Reuters Health in an email.

The findings, which are based on a mathematical model, showed life expectancy varied by only a few days between people who continued getting colonoscopies every ten years and those who chose annual fecal blood tests and other less-invasive alternatives.

"The best test for you depends on your risk, your preferences, and which screening approach you are willing and able to adhere to, since no screening is effective unless it's done," she added.

"Patients should talk with their doctors to decide which test is best for them."

Knudsen's team fed colon cancer screening and survival data into a National Cancer Institute (NCI) model, starting with hypothetical study participants that had a negative colonoscopy at age 50.

The researchers found that with no further screening, 31 out of every 1,000 people would be diagnosed with colon cancer during their lives and 12 would die from it. For people who continued having colonoscopies every ten years, that would fall to eight colon cancer diagnoses and two deaths per 1,000 people.

With annual fecal tests starting at age 60, Knudsen and her colleagues calculated that 11 to 13 out of every 1,000 people would get colon cancer, and three or four would die.

And with the last screening method, known as computed tomographic colonography, or CTC, nine people would be diagnosed with cancer and three would die if the tests were done every five years. Like colonoscopy, CTC requires bowel preparation, but otherwise is not as invasive.

The less-invasive screening methods would each cause about half as many complications as colonoscopy - affecting one percent of patients versus two percent, according to findings published Monday in the Annals of Internal Medicine. Those complications include bleeding and colon perforations.

"All of these methods will work if your ultimate goal is to reduce deaths from colon cancer," said gastroenterologist Dr. David Weinberg from Fox Chase Cancer Center in Philadelphia, who wrote an editorial accompanying the study.

PAYING A LOT MORE

According to the NCI, about 143,000 people are expected to be diagnosed with colon or rectal cancer in 2012, and close to 52,000 will die of the disease.

Weinberg said one of the advantages of colonoscopy is that it finds pre-cancerous polyps that can be removed before they turn into cancer.

Fecal blood tests, on the other hand, typically catch very early cancers, so more patients screened that way will get cancer and need treatment, although they'll have a good prognosis.

Colonoscopy is also more expensive than other options, at a bit over $1,000 a pop - and getting the procedure is typically not the most pleasant experience. A fecal test costs $20 to $50, and CTC about $500.

"If everybody gets a colonoscopy, you will have many fewer people who ever develop colon cancer, but you're going to pay a lot more money to get that effect," Weinberg told Reuters Health.

"What people and populations have to decide is, how do you want to spend your money?"

Although it's a limitation that the results are based on a mathematical model and not on screening and outcomes for real people, Weinberg said a comparable human study will likely never be done because of the time and money required.

Based on the available evidence, the United States Preventive Services Task Force, a government-backed panel, recommends screening for colon cancer using colonoscopy, sigmoidoscopy or fecal occult blood testing between age 50 and 75.

Although both colonoscopy and fecal blood tests are available most places in the U.S., other tests including CTC may be harder to find, or not reimbursed by insurance, according to Weinberg.

SOURCE: bitly.com/MnBiCA Annals of Internal Medicine, online November 5, 2012.

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