For patients with a positive fecal immunochemical test, the risk for colorectal cancer increases if diagnostic colonoscopy is delayed beyond 6 months, according to new research.

“In breast cancer, there are quality mandates from the federal government that say how quickly patients should be seen for certain tests. Colorectal cancer has not had that,” said senior investigator Douglas Corley, MD, PhD, from Kaiser Permanente in Oakland, California.

This study provides “a solid evidence-based structure” to direct patients and physicians in this follow-up and for the development of guidelines, he told Medscape Medical News.

Results from the study will be presented by Christopher Jensen, PhD, also from Kaiser Permanente in Oakland, here at Digestive Disease Week 2016.

The fecal immunochemical test is commonly used for colorectal cancer screening. Positive tests require a diagnostic colonoscopy, but little is known about the consequences of various follow-up intervals.

To evaluate time to colonoscopy and the risk for adverse outcomes, the researchers retrospectively analyzed members of the Kaiser Permanente Northern California and Southern California health plans. They identified 71,439 patients 50 to 75 years of age with positive fecal immunochemical tests.

The analyses were adjusted for demographic characteristics, body mass index, geographic location, and screening history.

The risks for any colorectal cancer and for higher-stage disease were similar when follow-up colonoscopy was done 8 to 30 days, 31 to 60 days, 61 to 90 days, or 91 to 180 after a positive test.

However, when colonoscopy was done 181 to 365 days after a positive test, the risk for higher-stage colorectal cancer was elevated, as was the risk for and any colorectal cancer.

And when colonoscopy was done beyond 365 days, the risk for higher-stage colorectal cancers more than doubled, as did the risk for any colorectal cancer.

Table. Odds Ratios for Colorectal Cancer by Time to Colonoscopy

For patients 61 to 75 years of age with few comorbidities, risk was elevated when the colonoscopy was done 91 to 180 days after a positive result (OR, 1.76; 95% CI, 1.04 – 2.99). This subgroup of patients has a high age-related risk for colorectal cancer and is less likely to have a false-positive result on the fecal immunochemical test.

Ideally, colonoscopy should be done in the 6 months after a positive test, said Dr Corley. And for older people, it should be done in the 3 months after a positive test.

It makes sense that patients would undergo diagnostic colonoscopy as soon as possible after a positive fecal immunochemical test, but there are many factors that contribute to delays, Dr Corley explained.

“There is wide variation in reaction to positive fecal immunochemical tests. While some patients may be alarmed, others may view the need for colonoscopy as a burden in terms of bowel prep, time off work, and so forth,” he told Medscape Medical News.

In many places, the logistics of the healthcare system can also be a burden, and multiple contact points between patients, primary care physicians, and gastroenterologists can be required, Dr Corley said.

“Each step may take days to weeks, and cumulatively, between the positive test and completion of colonoscopy, a substantial amount of time can elapse. Along the way, there is always the potential for the next step not to happen,” he pointed out.

At Kaiser Permanente, the process speeds along because the fecal immunochemical test report is sent straight to the gastroenterology division, where the appointment is initiated.

“We try to take out the intermediate steps,” Dr Corley said. “A lot of other systems don’t have such processes in place, to get patients into colonoscopy sooner, because data showing the problem with delays have been lacking.”

This “important study” addresses an information gap, said Linda Rabeneck, MD, vice president of prevention and cancer control at Cancer Care Ontario, and professor of medicine, health policy, management, and evaluation at the University of Toronto.

“The findings are important for both organized colorectal cancer screening programs, such as the one at Kaiser Permanente, and a program such as ours in Ontario,” Dr Rabeneck told Medscape Medical News.

“In organized screening, we have the opportunity to measure the time interval between an abnormal stool test (fecal immunochemical or occult blood test) and receipt of colonoscopy. We set out targets and then measure and report on our performance against the targets,” she explained.

New information from this large study provides evidence-based guidance in terms of setting the targets for completion of colonoscopy after an abnormal test, she pointed out. If targets are consistently not met, other steps (such as navigation or timed appointments) can be introduced to address the performance gap, she said.

In opportunistic screening, the importance of timely follow-up colonoscopy is clear as well, Dr Rabeneck explained. However, it can be more challenging to measure the time interval and to address any performance gaps because the necessary infrastructure to collect and report the information might be lacking.

“Endoscopists in practice may want to prioritize access to colonoscopy to those with a positive stool test,” she said.