In the analysis, the test was associated with "high sensitivity" for colorectal cancer, picking 84.5 percent of cancers in the first year of the study and 73 to 78 percent in subsequent years. (It's common for the first round of a screening program to detect more cancers.)
"This study provides additional support," said Corley, "that FIT can be an important tool for getting people screened that is both sensitive for picking up cancer and that people can comply with."
The study was published in the Annals of Internal Medicine and funded by a program of the National Cancer Institute.
National advocacy groups generally recommend that a person at average risk begin colorectal cancer screening at age 50. While colonoscopy is commonly referred to as a gold standard, it is not infallible. Both the colonoscopy and FIT have benefits and drawbacks.
Colonoscopy is an invasive test done once every 10 years for screening purposes. Many people find it unpleasant. The day before the procedure, the patient must cleanse the bowel by drinking a gallon or more of special solution. On the flip side, cancer can be prevented through colonoscopy, because non-cancerous polyps can be identified and removed. It is thought that many colon cancers begin as these polyps.
Because FIT is a non-invasive test, patients who choose this option forgo removal of non-cancerous polyps. Colon cancer is generally very slow-growing. While a single colonoscopy is more sensitive than a single FIT test, if a cancer is missed in the first year of FIT screening, it is likely to be picked up the next year. In addition, some colon cancers are very rapid-growing. It's possible that someone with a clean colonoscopy may develop a rapid-growing cancer in the 10 years before the next screening test. An annual FIT test would likely catch it.
If you opt for screening through the annual FIT, and you have a positive result, you'll need follow-up care, which is likely to include a colonoscopy.
But the big question is: How do the two tests compare in outcomes?
"The studies that have looked at how well (FIT) does compared to colonoscopy," said Corley, "suggest that they're fairly similar in preventing deaths from colon cancer."
While many people have heard of a colonoscopy, fewer patients and doctors are aware of FIT, said Robert Smith, vice president of cancer screening for the American Cancer Society, who was not affiliated with the study.
A "significant fraction" of people avoid colonoscopy, he said, but "when you give people options to screen, when you offer them a stool test or colonoscopy, a sizable fraction will choose stool test and complete it," he said.
This study demonstrates that an organized home-screening program was successful in screening many people who might otherwise not have come in for a colonoscopy.
"They're both very good tests," said Smith. Each has strength and limitations, but the stool testing should not be regarded as a second-class test as opposed to colonoscopy.
Kaiser's overall colon cancer screening rate is above 80 percent, Corley said, well above the national average of about 60 percent. "That's because we offer a variety of different tests so that people can complete the ones that are acceptable and work for them."
If the rest of the country reached an 80 percent screening rate for colorectal cancer, 200,000 deaths and 280,000 new colorectal cancer cases would be avoided by 2030, a previous study found. A national effort is underway to increase screening rates.
"The takeaway is, if you are 50 years of age and older, you need to be screened for colon cancer," Smith said. "If you are put off by colonoscopy, then (FIT) might be the right test for you."
