Aspirin users attending for NHS bowel cancer screening have less colorectal neoplasia: chemoprevention or false-positive faecal occult blood testing?

Objective: The NHS Bowel Cancer Screening Programme (BCSP) uses faecal occult blood (FOB) testing to select patients aged 60-69 years for colonoscopy.

Aim: To examine the association between aspirin use and the detection of colorectal neoplasia in screened patients undergoing colonoscopy.

Methods: Data were collected prospectively on individuals who underwent colonoscopy following a positive FOB test in the South of Tyne area between February 2007 and 2009. The relationship between the presence of colorectal neoplasia and age, gender, body mass index (BMI) and current aspirin use were evaluated using logistic regression analysis.

Results: 701 individuals underwent colonoscopy. 414 (59.1%) were male and 358 (51.1%) aged over 65 years. Males had a higher incidence of colorectal neoplasia (relative risk 2.26, 95% CI 1.65-3.10, p < 0.001). Current aspirin use was associated with a lower neoplasia detection rate (relative risk 0.79, 95% CI 0.50-0.98, p = 0.039). Increased age and BMI were not significantly associated with higher neoplasia detection.

Conclusion: Amongst individuals undergoing colonoscopy following a positive FOB test in the BCSP, current aspirin use was associated with a lower incidence of colorectal neoplasia. This may represent the chemopreventative effect of aspirin or increased false positivity of FOB testing. Further work is needed to clarify the contribution of each and could reduce the number of unnecessary colonoscopies.