FIT Completion and Yield Similar in Younger and Older Adults

Adults aged 45-49 years are as likely as those aged 50 years to complete a fecal immunochemical test (FIT) as an initial screen for colorectal cancer (CRC) and follow-up with a colonoscopy if needed, a new study has found.

The study also found a similar low 3% rate of CRC detected at colonoscopy in both the younger and older adults.

“Our study suggests that adults ages 45-49 have a colorectal cancer risk that is similar to what we see in adults age 50,” senior author Jeffrey K. Lee, MD, MPH, gastroenterologist and research scientist at Kaiser Permanente Northern California Division of Research (DOR) in Oakland, California, said in a news release.

“The low number of cancers we found also provides support for initially offering younger adults a non-invasive test, like FIT, to determine which patients would benefit from a colonoscopy,” Lee noted.

Timely and Important Question

“This study addresses a timely and important clinical question, namely, is FIT an acceptable screening modality in patients aged 45-49,” Ziad Gellad, MD, MPH, professor of medicine, Duke University Medical Center, Durham, North Carolina, who was not involved in the study, said in an interview.

“The finding that FIT completion and yield in younger patients is similar to those aged 50 and above is good news because it supports the use of this screening modality in the younger cohort,” said Gellad, section chief, gastroenterology, Durham VA Health Care System.

The study was published online in Annals of Internal Medicine.

In 2021, the US Preventive Services Task Force lowered the age to start CRC screening from 50 to 45 years, in response to studies showing an increased rate of CRC in adults aged 45-49 years.

The decision to start CRC screening at age 45 was made based on modeling studies, which are dependent on assumptions, co-first author Theodore R. Levin, MD, who is also a gastroenterologist and research scientist at Kaiser Permanente DOR, said in an interview.

“We thought it was important to collect real-world data on the experience of screening in this age group. We had no basis to know whether younger people would take up screening or if the yield of screening would be sufficiently high to warrant starting screening in this age group,” said Levin.

The researchers compared FIT screening completion and outcomes in 213,928 patients aged 45-49 years and 53,804 patients aged 50 years who received a FIT kit for the first time. The patients were from Kaiser Permanente Northern California, Washington, and Colorado.

Overall, FIT completion rates were slightly higher in the younger adults than in the 50-year-olds (38.9% vs 37.5%; adjusted risk ratio [aRR], 1.05), although the younger patients from Colorado were substantially less apt to complete a FIT (30.7% vs 40.2%; aRR, 0.77).

In the overall 45- to 49-year age group, 3.6% of adults had a positive FIT result, only slightly lower than the 4% positivity rate in the 50-year age group (aRR, 0.91).

About two thirds of adults in both groups who had a positive FIT result went on to have a colonoscopy within 3 months of receiving the test result.

Adenoma detection during colonoscopy was slightly lower in the younger than in the older group (58.8% vs 67.7%; aRR, 0.88). However, yields were similar for adenoma with advanced histology (13.2% vs 15.9%; aRR, 0.86), polyp with high-grade dysplasia (3.4% vs 5.1%; aRR, 0.68), sessile serrated lesion (10.3% vs 11.7%; aRR, 0.92), and CRC (2.8% vs 2.7%; aRR, 1.10).

FIT First Fits With Younger Adults’ Busy Lives

“Overall, people under 50 have lower incidence of cancer than people in their 50s, 60s, and 70s. However, if you do a test like FIT first, you can improve the yield of colonoscopy, which is a much more efficient strategy,” Levin said.

He noted that younger people are the least likely to be screened.

“They are busy with work and family responsibilities and may not realize that they are at risk for CRC. It is important to offer them a test that is easy to perform and does not require them to miss a day of work or arrange for a driver. They should be offered an option to screen with a stool-based test as an easy way to fit CRC screening into their busy lives,” Levin said.

Gellad said the study also highlights the limitations of FIT, “namely, that the low uptake and suboptimal colonoscopy follow-up of positive tests, also extend into the lower age group.”

Additionally, Gellad said he hopes other large systems will replicate this study to address the generalizability of these findings outside the Kaiser system.

The study was funded by the Kaiser Permanente Sydney R. Garfield Memorial Fund. Disclosures for study authors are available with the original article. Gellad consulted for Merck & Co. and Novo Nordisk and is a co-founder of Higgs Boson, Inc.