Colorectal cancer screening with fecal immunochemical testing: a community-based, cross-sectional study in average-risk individuals in Nigeria

Background: The estimated incidence of colorectal cancer is rising in Nigeria, where most patients present with advanced disease. Earlier detection of colorectal cancer is a goal of the Nigerian National Cancer Control Plan, but the utility of fecal-based screening is unclear. This study aimed to assess the fecal immunochemical test as a colorectal cancer screening modality in average-risk individualS in Nigeria.

Methods: A population-based, cross-sectional study of qualitative fecal immunochemical test-based colorectal cancer screening was done in asymptomatic, average-risk participants aged 45-75 years in three states in Nigeria (Osun, Kwara, and Lagos). Participants were invited to enrol using age-stratified and sex-stratified convenience sampling following community outreach. Exclusion criteria included a personal history of colorectal cancer or rectal bleeding in the previous 6 months, a first-degree relative with a known diagnosis of colorectal cancer, or a comorbidity that would preclude conscious sedation or general anesthesia. Participants with positive fecal immunochemical test results underwent colonoscopy, and the positive predictive value of fecal immunochemical testing for colorectal cancer and advanced adenomas (≥10 mm, tubulovillous or villous or high-grade dysplasia) was calculated. Data on demographics and acceptability of fecal immunochemical testing and colonoscopy were collected.

Findings: Between January and April 2021, 2330 participants were enrolled in the study and received a fecal immunochemical test, which was returned by 2109 participants. 1677 participants tested negative and 432 tested positive. Of these 432 participants, 285 underwent a colonoscopy (235 showed no polyps or cancer, 47 had polyps identified, and three had colorectal cancer identified). Of the 47 participants who had polyps identified, 20 had advanced adenomas diagnosed. The median age was 57 years (IQR 50-63), 958 (41%) were male and 1372 (59%) were female, and 68% had at least a secondary-level education. Participants were evenly spread across wealth quintiles. The positivity rate of the fecal immunochemical test was 21% overall (432 of 2109; 95% CI 20-21%), 11% (51 of 455; 95% CI 10-12) in Lagos, 20% (215 of 1052; 95% CI 20-21) in Osun, and 28% (166 of 597; 95% CI 27-29) in Kwara. Among the patients with a positive fecal immunochemical test who completed colonoscopy, the positive predictive value for invasive colorectal cancer was 1·1% (95% CI 0·3-3·3), and 7·0% (4·5-10·8) for advanced adenoma. The acceptability of fecal immunochemical screening among participants was very high.

Interpretation: Colorectal cancer screening with qualitative fecal immunochemical tests in Nigeria is feasible and acceptable to average-risk asymptomatic participants. However, the low positive predictive value for advanced neoplasia and high endoscopy burden investigating false positives suggests it might not be an appropriate screening tool in this setting.

Funding: Thompson Family Foundation, Prevent Cancer Foundation, National Institutes of Health/National Cancer Institute Program Cancer Center.