Waiting up to nine months after a positive fecal immunochemical test (FIT) to have a follow-up colonoscopy is not associated with an increased risk of colorectal cancer according to a large study published online this week in the Journal of the American Medical Association (JAMA).
But waiting longer than nine months does increase the risk — as well as the risk of having advanced-stage disease when the cancer is diagnosed, the study found.
“With this study we have strong evidence that a colonoscopy should be performed within several months of a positive fecal screening test,” said lead author Dr. Douglas Corley, a gastroenterologist and research scientist at Kaiser Permanente in San Francisco, in a released statement.
A recommended option
Colorectal cancer — cancer of the colon or rectum — is the second leading cause of cancer-related deaths in the United States, and the third most common cancer among both men and women, according to the Centers for Disease Control and Prevention. Each year, about 136,000 Americans are diagnosed with the disease, and about 52,000 die from it.
FIT is widely used around the world for colorectal cancer screening, although less so here in the United States, where colonoscopies are more common. In recent years, however, Americans have begun to use FIT more frequently, due largely to its effectiveness, low cost and ease-of-use. (The test can be done at home and then mailed to a laboratory.) The U.S. Preventive Services Task Force includes the annual FIT among its recommended screening methods for colorectal cancer.
If the results of a FIT come back positive, the patient must have a follow-up colon examination, usually a colonoscopy. During the colonoscopy, the doctor performing it will look for and possibly remove any cancerous or pre-cancerous polyps.
Recommendations for how quickly that follow-up exam should take place have varied, however, due to a lack of good, strong evidence. The current study set out to gather that evidence.
For the study, Corley and his colleagues examined the medical records of 70,124 Kaiser Permanente patients between the ages of 50 and 75 (the ages for which colorectal cancer screening is recommended) who received a positive FIT result between 2010 and 2013. Among those patients, 2,191 were eventually diagnosed with colorectal cancer, including 601 cases of advanced-stage disease.
The researchers then compared the cancer diagnostic outcomes for patients who received a follow-up colonoscopy within eight to 30 days with those who had received it within various later timeframes.
They found no significant differences in the risk for colorectal cancer or for the risk of that cancer being advanced when the follow-up colonoscopy was done within nine months. But if the follow-up was done 10 to 12 months after a positive FIT result, the risk of being diagnosed with colorectal cancer increased by about 50 percent, and the risk of having advanced disease almost doubled.
For people who waited longer than 12 months, the risks were even higher: Those individuals were twice as likely to be diagnosed with colorectal cancer and three times as likely to be diagnosed with advanced disease.
‘As soon as feasible’
The researchers make clear in their study that these results do not prove a causal relationship between delaying the follow-up colonoscopy past nine months and a greater risk of being diagnosed with the colorectal cancer. Other factors, not yet identified, may explain their study’s results, they stress.
But the researchers do say that their study’s findings “raise the possibility that by the time a lesion is detectable by FIT, further lesion progression might occur as soon as 6 to 12 months after a positive FIT result.”
One of the study’s co-authors, Kaiser Permanente gastroenterologist Dr. Theodore Levin, says the findings should be reassuring to patients who receive a positive FIT result and are unable to immediately have the follow-up colonoscopy.
“It is a lot of effort for patients to arrange a colonoscopy, given the need for time off work and scheduling someone to accompany them home,” he said in the released statement. “Our study shows that you should get your colonoscopy done, and you should do it s soon as is feasible.”
But any time within a few months, he adds, “is reasonably safe based on these data.”
FMI: You’ll find an abstract of the study on the JAMA website, but the full study is behind a paywall.