High diagnostic accuracy with simple, at-home test for colorectal cancer
Tests that require patients to collect a single stool sample at home and then send it to a lab for analysis will detect about 79% of colorectal cancers, according to a new evidence review. The review of 19 studies examining eight different fecal immunochemical tests (FITs) also finds that the tests will correctly identify about 94% of patients who do not have cancers of the rectum or colon.
"We know the FIT is easy to use, and now we also know that it is a great tool for assessing which patients have cancer and which patients don't," said Beth Liles, MD, review coauthor and clinical investigator at the Kaiser Permanente Center for Health Research located in Portland, Oregon. The review was published in the Annals of Internal Medicine (2014;160:171-181).
Colorectal cancer is the second leading cause of cancer death in the United States, according to the Centers for Disease Control and Prevention. Yet one in three adults is not adequately screened.
"FIT is simple, can be done at home, and can save lives," said lead author Jeffrey Lee, MD, MAS, at the Kaiser Permanente Division of Research in Oakland, California, and the University of California, San Francisco. "The American Cancer Society and other professional organizations have recommended FIT as a screening tool for colorectal cancer since 2008, but there are still many people who don't know about it."
The US Preventive Services Task Force recommends that people with normal risk for colorectal cancer should begin screening at age 50 years and end at age 75 years. Unlike older stool tests, FIT does not require people to restrict their diets or to stop taking medications. Conducted annually, the test detects small amounts of blood in the stool, and people who test positive are much more likely to have colorectal cancer. People who have a positive FIT need a follow-up colonoscopy to look for cancer or precancerous polyps.
Other screening options for colorectal cancer include sigmoidoscopy, which involves physical examination of the lower colon, or colonoscopy, which examines the entire colon.
The evidence review found that the FITs were fairly sensitive. On average, the tests detected 79%, or about 4 of 5 cancers with only one round of testing. The tests were also highly specific: on average, 94% of people who did not have cancer tested negative with a single FIT.
By comparison, studies indicate that another at-home test called fecal occult blood test (FOBT) detects only about 13% to 50% of cancers after a single round of testing. The FOBT is the predecessor to FIT and requires three stool samples as well as medication and dietary restrictions.
According to the evidence review, no single FIT performed markedly better than another, but the authors caution that there was only one study comparing brands head-to-head. Most of the FITs required collection of only one stool sample. Surprisingly, the authors found that brands requiring two or three stool samples were no more accurate than those requiring only one sample.