NEW YORK (360Dx) – The fecal immunochemical test could help diagnose patients with colorectal cancer whose initial symptoms are equivocal, according to a new study.
About half of colorectal cancer patients present with symptoms that are also often associated with benign conditions. As opposed to more alarming symptoms that get patients sent off quickly for colonoscopy, these low-risk, or "non-alarm," symptoms more often trigger a "wait and see" approach, the authors of the new study said.
The team of researchers led by Aarhus University's Peter Vedsted investigated whether the fecal immunochemical test (FIT) — which detects trace amounts of blood in the stool — could help diagnose colorectal cancer among patients with such non-alarm symptoms in a general practice setting. As they reported in the British Journal of Cancer today, the researchers found FIT to have a low false negative rate for detecting colorectal cancer.
"Our results suggest that the FIT may be used as a rule-in test in this group of patients," Vedsted and his colleagues wrote in their paper.
For their prospective cohort study, the researchers focused on a region of Denmark where the FIT had recently been introduced. They monitored the number of tests requested by the 853 general practitioners there and patients' outcomes.
While physicians were to use their clinical judgment as to whether a patient should get an FIT, they were given guidelines that suggested non-alarm symptoms like unexplained anemia, change in bowel habits, or abdominal pain should merit testing. That way, the researchers said, their study would more likely resemble how FIT testing would be used and be generalizable to the Danish healthcare system.
In the study timeframe, the physicians ordered nearly 3,500 FITs. Of these, 84.4 percent came back negative and 15.6 percent were positive.
In the three months after testing, diagnostic investigations such as a colonoscopy or CT colonography were performed in 14 percent of those with negative results and 77 percent of those with positive results. Of those with positive FIT, 9.4 percent were later diagnosed with colorectal cancer and 13.5 percent were diagnosed with serious bowel disease like inflammatory bowel disease or high-risk adenomas within three months.
Most of the colorectal cancers diagnosed after a positive FIT were stage I or stage II. In addition, slightly more than 40 percent of cancers were in the proximal colon, a region where tumors are typically linked to poorer prognosis. This suggested to the researchers that FIT might be able to help catch proximal colon tumors early on.
Meanwhile, less than .1 percent of patients with negative FIT were later diagnosed with colorectal cancer and less than .9 percent of negative FIT patients were diagnosed with serious bowel disease.
When physicians requested FIT, Vedsted and his colleagues estimated the positive predictive value for colorectal cancer to be 1.5 percent. If the FIT was positive the PPV was 9.4 percent. They noted that these figures could be swayed by the 23 percent of individuals with a positive FIT that didn't have a diagnostic investigation.
In 2015, the UK's National Institute for Health and Care Excellence updated its guidelines to indicate that patients with low-risk symptoms be evaluated via occult blood stool testing — namely by the older guaiac fecal occult blood test (gFOBT) — a move Vedsted and his colleagues noted was criticized. The guidelines were updated in 2017 to suggest the use of FIT, and the researchers argued that their new results support its use in patients with low-risk symptoms.
"[W]e consider the findings of importance in a realistic diagnostic workup of patients with non-alarm symptoms of [colorectal cancer] and it reveals a possible diagnostic supplement for a group of patients that are notoriously difficult to handle in primary care," Vedsted and his colleagues wrote.