Association Between Time to Colonoscopy After Abnormal Fecal Immunochemical Test and Risk of Adenoma, Advanced Colorectal Neoplasia and Colorectal Cancer Incidence

Objective: Colorectal cancer (CRC) is a significant health concern in Thailand, with high incidence and late-stage diagnosis rates. This study investigates the timing of colonoscopy following a positive fecal immunochemical test (FIT) and identifies risk factors for colorectal neoplasms. Material and Methods: A retrospective analysis included Thai patients aged 50-75 with a positive FIT who underwent colonoscopy. Exclusions were made for prior colonoscopy, colorectal surgery history, hereditary syndromes, inflammatory bowel disease, and incomplete pathology reports. Data from January 2018 to December 2021 were assessed for demographics, colonoscopy findings, and pathology outcomes. Results: The study encompassed 2,717 participants with balanced age and gender distributions. Preliminary risk factors associated with the development of adenoma and advanced colorectal neoplasia (ACRN) included age [odds ratio (OR): 1.03, 95% confidence interval (CI): 1.02-1.05, p-value<0.001], gender (OR for males: 1.60 for adenoma, 1.69 for ACRN, p-value<0.001), and smoking (OR: 1.92, p-value=0.001). The timing of colonoscopy within one-year post-FIT did not exhibit statistically significant associations with adenoma, ACRN, or CRC. Conclusion: This study provides valuable insights into CRC screening in Thailand. It suggests that timing within a year of colonoscopy might not be the sole determinant of improved outcomes post-FIT. Preliminary risk factors encompassed age, gender, and smoking. Future studies should focus on larger cohorts to investigate adverse outcomes, such as late-stage CRC and CRC-related mortality.