Stool Test Effective for Detecting Colon Cancer
Colonoscopy still preferred screening, but this offers less invasive option, researchers say
By Dennis Thompson
MONDAY, Jan. 25, 2016 (HealthDay News) -- Tests for blood in the stool can consistently detect colon cancer when used on an annual basis, and they are effective even in the second, third and fourth years of screening, a new study says.
The researchers said these findings suggest that the stool test could be a reasonable screening alternative to colonoscopy -- currently considered the gold standard for colon cancer screening.
Known as fecal immunochemical tests, experts examine stool samples for microscopic amounts of blood shed by colon tumors, explained study co-author Dr. Douglas Corley, a research scientist with Kaiser Permanente in Oakland, Calif.
Doctors have been concerned that fecal blood tests might become less effective over time, hampering their usefulness as a screening tool, he said.
Colon tumors or precancerous polyps have to be large to start releasing blood into a person's stool, Corley said. So, if all large tumors and polyps were detected and removed during the first year of screening, the concern was there might be a large drop-off in cancer detection during subsequent years, he added.
To see whether that would happen, researchers tracked annual fecal blood tests performed on nearly 325,000 Kaiser Permanente patients in California during a four-year period.
The first year of screening with fecal blood tests detected colon cancer in 84.5 percent of participants who were diagnosed with the disease, the study reported.
"We found that the sensitivity for cancer was somewhat higher in the first year, and that's not surprising," Corley said. "The first year you screen someone, for breast cancer or for anything, you're going to find cancers that have been there for a while that may be larger or are easier to detect."
However, the effectiveness of the fecal blood test varied between 73 percent and 78 percent in years two through four. That means the test remained capable of picking up new tumors as they grew to a detectible size, the researchers said.
The findings were published Jan. 25 in the Annals of Internal Medicine.