Colonoscopy: once at age 66 suffices if FIT is done every 1-2 years

Colonoscopy for colorectal cancer screening can be limited to once at age 66 if a fecal immunological test (FIT) for occult blood is performed annually or biannually according to a study just published in Clinical Gastroenterology and Hepatology. This spares cost, not to mention discomfort and inconvenience. The authors state:

"Colorectal cancer (CRC) screening guidelines recommend screening schedules for each single type of test except for concurrent sigmoidoscopy and fecal occult blood test (FOBT)...Currently, most CRC screening guidelines recommend screening schedules for average-risk adults that are based on a single type of test (with the exception of concurrent sigmoidoscopy/fecal occult blood test [FOBT]), eg, colonoscopy every 10 years or a stool test (gFOBT or FIT) every year. A screening strategy that combines annual or biennial FIT at younger ages and colonoscopy at older ages may offer the potential to deliver optimal health benefits at a lower cost and risk of complications, while taking into consideration increasing risk for CRC at older ages... In the present study, we used the Archimedes Model to compare the cost-effectiveness of a hybrid CRC screening strategy, by using annual FIT at younger ages (50–65 years) combined with a single colonoscopy at age 66, against other screening strategies in a population representative of KPNC members during a 30-year period."

They applied the Archimedes Model, derived in this case from public databases, published epidemiologic studies, and clinical trials relevant to colorectal cancer, to evaluate the effects of different CRC screening strategies in patients of Kaiser Permanente Northern California. The hybrid screening strategy did very well:

"A hybrid screening strategy led to substantial reductions in CRC incidence and mortality, gains in quality-adjusted life years (QALYs), and reductions in costs, comparable with those of the best single-test strategies. Screening by annual FIT of patients 50–65 years old and then a single colonoscopy when they were 66 years old (FIT/COLOx1) reduced CRC incidence by 72% and gained 110 QALYs for every 1000 people during a period of 30 years, compared with no screening. Compared with annual FIT, FIT/COLOx1 gained 1400 QALYs/100,000 persons at an incremental cost of $9700/QALY gained and required 55% fewer FITs. Compared with FIT/COLOx1, colonoscopy at 10-year intervals gained 500 QALYs/100,000 at an incremental cost of $35,100/QALY gained but required 37% more colonoscopies."

Should the FIT be done yearly or every 2 years?

"Changing the screening interval for FIT from 1 year to 2 years did not reduce the benefits of hybrid screening significantly. This is probably because for hybrid screening, FIT screening occurs between ages 50 and 65, when the incidence of CRC is relatively low compared with older ages."

That colonoscopy at age 66 is crucial though:

"Adherence to colonoscopy at age 66 is critical to maintain the effectiveness of the hybrid screening programs. If compliance to colonoscopy at age 66 were only 50%, the QALY gains and cost savings of FIT/COLOx1 compared with no screening would be reduced by 28% and 41%, respectively."

Experienced clinicians know that laboratory reference ranges are often too broad, and should note that a more sensitive range for the FIT than the usual 100 ng Hb/mL is important:

"We estimated the sensitivity and specificity of FIT with a 50 ng Hb/mL cutoff from limited data available at the time of the analysis. Increasing the sensitivity and decreasing the specificity of FIT by using a 50 ng Hb/mL cutoff led to modest increases in the QALY gains and cost savings of FIT/COLOx1. Most interestingly, FIT/COLOx1 that used a 50 ng Hb/mL cutoff outperformed screening by colonoscopy in both health benefits and costs. This suggests that a hybrid screening strategy that uses a cutoff of 50 ng Hb/mL for FIT might be optimal..."

It should be understood that a history of polyps and other risk factors may mandate additional colonoscopies. Bhe authors' conclusion offers a practical guideline for the use of colonoscopy and FIT for routine colorectal cancer screening:

"In our simulation model, a strategy of annual or biennial FIT, beginning when patients are 50 years old, with a single colonoscopy when they are 66 years old, delivers clinical and economic outcomes similar to those of CRC screening by single-modality strategies, with a favorable impact on resources demand."