Effects of Increasing Screening Age and Fecal Hemoglobin Cutoff Concentrations in a Colorectal Cancer Screening Program

Abstract

Background & aims: Several countries have implemented programs to screen for colorectal cancer (CRC) by using the fecal immunochemical test (FIT). These programs vary considerably in age of the population screened and the cutoff concentration of fecal hemoglobin (Hb) used to identify candidates for further evaluation; these variations are usually based on a country's colonoscopy resources. We calculated how increasing the Hb cutoff concentration and screening age affects colonoscopy yield, missed lesions, and demand.

Methods: We collected data from 10,008 average-risk individuals in The Netherlands, 50-74 years old, who were invited for an FIT in the first round of a population-based CRC screening program from November 2006 through December 2008. Fecal samples were collected, and levels of Hb were measured by using the OC-sensor Micro analyzer; concentrations ≥10 μg Hb/g feces were considered positive. Subjects with a positive FIT were scheduled for colonoscopy within 4 weeks. Logistic regression analysis was performed to evaluate the association between age and detection of advanced neoplasia.

Results: In total, 5986 individuals (62%) participated in the study; 503 (8.4%) had a positive test result. Attendance, positive test results, detection of advanced neoplasia, and the FIT's positive predictive value all increased significantly with age (P < .001). Detection of advanced neoplasia ranged from 1.3% in the youngest age group to 6.2% in the oldest group; the positive predictive value of the FIT was 26% in the youngest group and 47% in the oldest group. Increasing the starting age of invitees from 50-74 years to 55-74 years reduced the proportion of subjects who underwent colonoscopy evaluation by 14% and resulted in 9% more subjects with advanced neoplasia being missed. Increasing the cutoff concentration from 10 to 15 μg Hb/g feces reduced the proportion of subjects who underwent colonoscopy evaluation by 11% and resulted in 6% of advanced neoplasia being missed.

Conclusions: In an analysis of an average-risk screening population in The Netherlands, we found that detection of advanced neoplasia by FIT increases significantly with age and fecal Hb cutoff concentration. Increasing the cutoff concentration or screening age reduces the numbers of patients who undergo colonoscopy evaluation in FIT-based CRC screening programs. Our findings provide insight in these effects per age category and cutoff concentration and the consequences in terms of missed lesions.

Keywords: Colon Cancer; Colorectal Adenoma; Early Detection; Fecal Occult Blood; Mass Screening.