Low incidence of interval colorectal cancer seen with FIT screening

Last Updated: 2017-05-29

By Will Boggs MD

NEW YORK (Reuters Health) - Screening with a fecal immunochemical test (FIT) is associated with a low incidence of interval colorectal cancer (CRC), researchers from the Netherlands report.

"In our study, survival of persons with a fecal immunochemical test (FIT) interval cancer (e.g., a cancer diagnosed between screening rounds after negative FIT before the next FIT is due) was comparable to survival of persons with a screen-detected CRC and better than that of non-participants and the general population,” said Dr. Manon van der Vlugt from Academic Medical Center in Amsterdam.

“This is an important finding for FIT-based screening programs,” she told Reuters Health by email.

Dr. van der Vlugt’s team report FIT interval cancers over multiple rounds of FIT screening in their study of more than 27,000 individuals, 69% of whom underwent FIT screening at least once.

The FIT interval cancer rate was 23%, reflecting a FIT sensitivity for detecting CRC of 77%.

“The interval-cancer proportion is much lower than the previously reported interval-cancer proportions for guaiac-based fecal occult blood testing (gFOBT) of 48-55%, so FIT-based screening will indeed result in a lower number of interval cancers,” Dr. van der Vlugt said. “This conclusion needs to be made with caution, as we did not perform a head-to-head comparison study over 10 years.”

Screen-detected CRC (those detected at colonoscopy following a positive FIT result), FIT interval cancers, and CRC in those who didn't participate in screening were mostly located in the distal colon, whereas colonoscopy interval cancers were more often located in the proximal colon.

“In our cohort, the small number of colonoscopy interval cancers were mainly located in the proximal colon,” Dr. van der Vlugt said. “This suggests that this might be due to shortcoming of the colonoscopy procedure, i.e., missed lesions due to poor bowel preparation or no cecal intubation.”

Survival was lowest in those with colonoscopy interval cancers at 24 months (67% vs. 85% for FIT interval cancers and 93% for screen-detected CRC) and at 36 months (56% vs. 85% and 91%, respectively).

“As persons diagnosed with CRC within a FIT-based CRC screening program have better CRC-stage distribution and less all-cause mortality, physicians should stimulate/advise their patients to participate in a FIT-based CRC screening program,” Dr. van der Vlugt said. “However, we should also realize that FIT is not perfect, and neither is the follow-up colonoscopy. If a patient develops abdominal symptoms that could fit with colorectal cancer, despite a recent negative FIT or colonoscopy, additional investigations are necessary and he/she should consult their doctor.”

“As health physicians, we are afraid that we might falsely reassure screening participants who received a negative test result of the FIT,” she explained. “These persons might not consult or delay their visit to the GP if they develop symptoms of colorectal cancer in a later phase, thereby causing a delay in diagnosis (and) treatment, and potentially harming clinical outcome. Based on the results of our study, this theoretical risk does not have an immediate negative effect on all-cause mortality in 10 years of a FIT-based screening program.”

Dr. Joaquin Cubiella from Complexo Hospitalario Universitario de Ourense, in Spain, who has compared colonoscopy and FIT-based CRC screening programs, told Reuters Health by email, “The evidence favoring FIT is quite extensive at this moment (acceptance, sensitivity for CRC, sensitivity for advanced adenomas) besides the simplification in handling the samples and the option to decide the threshold to determine a positive test.”

“CRC screening programs must implement quality-control policies in order to reduce the colonoscopy interval cancers,” said Dr. Cubiella, who was not involved in the new work.

Dr. Chyke A. Doubeni from the University of Pennsylvania, in Philadelphia, who has also studied CRC screening, said, “FIT is an effective screening test for CRC, should be offered to patients as an option, and should replace guaiac FOBT. The programmatic sensitivity of FIT appears better than what has been previously report for guaiac FOBT (77% vs. approx 50%).”

“FIT should be performed annually,” Dr. Doubeni told Reuters Health by email. “It is really important that patients undergo colonoscopy promptly if the FIT is positive. Patients should be made aware that like most tests used in clinical practice, FIT is not perfect and those who develop conditions such as change in bowel habits, rectal bleeding, unexplained weight loss, iron deficiency anemia, or a mass or swelling in the abdomen, should see their doctors even if they have had a negative FIT.”

Dr. Doubeni, who was not involved in the new study, added, “The test is not appropriate for those at increased risk because of having a strong family history, particularly in first-degree relatively, and other conditions such as inflammatory bowel disease. Those should see their doctor to discuss their options.”

SOURCE: http://bit.ly/2s6c4TA

Gastroenterology 2017.