Interval Advanced Adenomas and Neoplasia in Patients with Negative Colonoscopy Following Positive Stool-Based Colorectal Cancer Screening Test.

Background/aims: Fecal occult blood test (FOBT) and fecal immunohistochemical test (FIT) are used for colorectal cancer (CRC) screening. However, when no adenomas are found following a positive FOBT/FIT, the future risk of advanced adenomas or colorectal cancer (CRC) is unclear. We determined the incidence and determinants of advanced adenomas or CRC after a negative index colonoscopy following a positive FOBT/FIT.

Methods: We identified patients in the Harris Health System (Houston, Texas) who underwent a colonoscopy following a positive FOBT/FIT from 01/2010 to 01/2013. We compared the incidence rates of advanced adenomas (≥ 1 cm, villous histopathology, or high-grade dysplasia) or CRC through 12/2023 for patients without polyps on index colonoscopy (negative colonoscopy) to patients with polyps (positive colonoscopy). We examined risk factors for incident adenomas using Cox regression models.

Results: Of 2096 patients, 1293 (61.7%) had negative index colonoscopy and 803 (38.3%) had positive index colonoscopy. Overall, 411 patients (19.6%) underwent subsequent colonoscopy with incident adenomas in 241 patients and no incident CRC over mean 12.5 years. The incidence rate of advanced adenomas was 2.08 per 100 person-years after positive index colonoscopy compared to 0.65 per 100 person-years after negative index colonoscopy (age-adjusted incidence rate ratio 3.08, 95% CI 1.27-7.48). Non-Hispanic white race was the strongest risk factor for incident adenomas among patients with negative index colonoscopy.

Conclusions: We found a low likelihood of advanced adenomas and no interval CRC following negative index colonoscopy after positive FOBT/FIT. Non-Hispanic white race was a risk factor for incident adenomas, and these patients may warrant closer surveillance.