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False FIT results common with small, nonpolypoid colorectal adenomas, early cancer
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Patients with early-stage colorectal cancer or small or nonpolypoid adenomas are more likely to receive false-negative results from fecal immunochemical testing, according to recent results.
Researchers evaluated data from 18,296 patients aged older than 50 years (mean age, 59.8 years) who underwent screening colonoscopy and fecal immunochemical testing (FIT) in Taiwan between September 2005 and September 2010. The cohort included 4,045 patients with colorectal neoplasms, including 632 advanced adenomas, 28 patients with cancer and 23 with invasive cancer.
Colonoscopy also revealed nonadvanced adenomas in 3,385 participants, while FIT positivity was observed in 1,330 cases. FIT had a sensitivity of 78.6% (58.5%-91%) for the detection of cancer, 28% (24.6%-31.7%) for advanced adenomas and 10.6% (10.2%-12.3%) for nonadvanced adenomas. Sensitivity was stage-dependent, and increased from 28% for advanced adenomas to 66.7% for T1 cancers and carcinoma in situ, and 100% for stages T2 through T4 (P<.001 for trend).
Multivariate analysis, adjusting for potential confounders, demographic information and colonoscopy results, indicated a significant association between false-negative FIT results and proximal neoplasm location (adjusted OR=1.27; 95% CI, 1.01-1.59) and an inverse association with lesion size (aOR=0.9; 95% CI, 0.88-0.92 per 1 mm increase).
Among nonadvanced adenomas, false negatives were associated with adenoma size smaller than 5 mm (aOR=1.57; 95% CI, 1.24-1.98) and inversely associated with synchronous location (aOR=0.7; 95% CI, 0.5-0.99). Advanced adenomas smaller than 15 mm also were significantly associated with false negatives (aOR=2.85; 95% CI, 1.79-4.54) as were nonpolypoid lesions (aOR=2.15; 95% CI, 1.22-3.8).
“Improving the sensitivity of the fecal tests, especially to early advanced neoplasms, could increase the effectiveness of CRC screening programs,” the researchers wrote. “Our findings suggest that the benefits of a single FIT screening may differ on the basis of tumor characteristics and highlighted the existence of lower FIT performance in subgroups. These findings also highlight the importance of future studies exploring whether this limitation really leads to less protection against proximal colon cancer in FIT-based screening programs.”
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