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April 29, 2019
A recently published review of data from thirty-one colon cancer screening studies shows that an annual at-home stool test called a fecal immunochemical test (FIT) may be as effective as a colonoscopy at detecting cancer in average-risk adults. While the data review adds support for colon cancer screening with inexpensive and non-invasive stool tests, authors of the study recommend patients discuss with their healthcare practitioners their risk for developing colon cancer and whether an annual stool test is appropriate for them.
Colorectal cancer (also called colon cancer) is the second leading cause of cancer deaths in the United States. A colonoscopy is currently the "gold standard" for colon cancer screening in the U.S. and some healthcare practitioners may recommend it over other testing options. However, FIT is considered a suitable alternative by most U.S. health organizations. In other countries, a colonoscopy is only performed if an average-risk adult receives a positive result from an FIT.
Many patients experience anxiety and fear prior to a colonoscopy, which can often deter some from having the screening done in a timely fashion or even at all. Currently, about 35% of people who should get a colonoscopy do not. It should be noted that colonoscopies are not entirely without risk and can rarely result in serious injuries like a perforated colon.
FIT, on the other hand, has close to no risk for injury and often do not cause the same level of anxiety as preparing to have a colonoscopy, which may encourage more people to get screened for colon cancer. Though less expensive and less invasive than colonoscopies, FIT needs to be repeated annually. Colonoscopies are recommended for colon cancer screening every 10 years.
Most health institutions that offer guidelines for colon cancer screening show no preference for FIT or colonoscopy. The American Cancer Society recognizes there are pros and cons for different types of screening tests but says that "the most important thing is to get screened, no matter which test you choose." (For details on colon cancer screening recommendations, see the screening articles for Adults and Adults 50 and Up)
According to the authors of the review, their main objective was to evaluate the use of annual FITs for colon cancer screening in average-risk adults in the United States. FIT measures the presence of hemoglobin, a protein normally found in red blood cells. The presence of hemoglobin in a stool sample may indicate bleeding in the digestive tract, a sign often associated with colon cancer.
The review, published on February 23, 2019 in the Annals of Internal Medicine, looked at data from 31 colon cancer-screening studies with a total of 120,255 asymptomatic, average-risk adult participants who received FIT and a follow-up colonoscopy. The review authors defined "average risk for developing colon cancer" as having no family history of colon cancer, no personal history of inflammatory bowel disease, and no previous colon cancer or pre-cancerous polyps (for example, advanced adenomas).
The authors found that for this population, FIT had a moderate to high detection rate for colon cancer when compared to colonoscopy. Several thresholds reflecting the amount of blood present in the stool sample were identified. Based on these thresholds, sensitivity (true positive rate) in detecting colon cancer ranged from 71% to 91%. FIT was able to rule out colon cancer (specificity or true negative rate) 90% to 95% of the time when colonoscopies were negative. FIT sensitivity and specificity for advanced adenomas in the colon or rectum were lower, but many of these benign polyps never turn into cancer.
Referring to these data analyses, lead author Dr. Thomas Imperiale said in a press release: "If annual FIT results remain negative, FIT buys you time until a colonoscopy may be required, and it could be the case that a colonoscopy for screening may never be necessary or required."
An editorial about this study emphasizes the importance of screening and the value of using FIT. It calls for more information to be shared with patients and healthcare practitioners about the use of annual FIT for colon cancer screening and assurances that FIT is not a "second-best" or less than "gold standard" strategy for average-risk individuals. FIT might also be a better option for colon cancer screening in people under 50 years old because it is still unlikely that insurers will cover colonoscopies for this younger population.