Long Delay From Positive Fecal Test to Colonoscopy May Increase CRC Risk

April 25, 2017

A delay of 10 months or longer between a positive fecal immunochemical test and a follow-up colonoscopy was associated with a higher risk of colorectal cancer.

A delay of 10 months or longer between a positive fecal immunochemical test (FIT) and a follow-up colonoscopy was associated with a higher risk of colorectal cancer (CRC) and with more advanced-stage disease at the time of diagnosis, according to a large retrospective review study. Delays of fewer than 10 months were not associated with any increased risk compared with a rapidly conducted colonoscopy.

“A positive FIT result needs to be followed by a complete colon examination, typically with colonoscopy,” wrote study authors led by Douglas A. Corley, MD, PhD, of the division of research at Kaiser Permanente Northern California in Oakland. “However, recommendations for how quickly to complete follow-up differ and lack a strong evidence base.”

The researchers conducted a retrospective cohort study with Kaiser Permanente Northern and Southern California, including 70,124 patients with a positive FIT result between January 2010 and December 2014. In that group, there were 2,191 cases of any CRC, and 601 cases of advanced-stage disease at diagnosis. The results of an analysis comparing the timing of the follow-up colonoscopy were published in JAMA.

Using a colonoscopy follow-up within 8 to 30 days after positive FIT results as a reference (27,176 patients), each 30-day interval beyond that was associated with a 3% increased risk of CRC, and a 5% increased risk of advanced disease; this relationship was not linear, however. For follow-up that took place between 2 and 3 months later, 4 to 6 months later, and 7 to 9 months later, there was no significant difference in CRC cases per 1,000 patients.

In patients who had their follow-up examination 10 to 12 months after a positive FIT result (748 patients), the odds ratio (OR) for CRC was 1.48 compared with the patients who waited 8 to 30 days (95% CI, 1.05–2.08); there were 49 cases per 1,000 patients, compared with 30 per 1,000 patients in the early follow-up group. The OR for advanced-stage disease in the 10–12 months group was 1.97 (95% CI, 1.14–3.42). For patients whose follow-up was more than 12 months from the positive FIT result, the ORs for CRC and advanced disease were 2.25 (95% CI, 1.89–2.68) and 3.22 (95% CI, 2.44–4.25), respectively.

The authors wrote that further research is still needed to determine if this relationship between delayed colonoscopy and increased risk is causal. In an accompanying editorial, Carolyn M. Rutter, PhD, of the RAND Corporation in Santa Monica, California, and John M. Inadomi, MD, of the University of Washington School of Medicine in Seattle, wrote that “sooner is probably better for follow-up colonoscopy because cancer risk increases over time, but increases slowly.” They added that from a practical standpoint, a shorter interval likely reduces the risk of losing contact with patients.