Fecal immunochemical tests offer an effective, noninvasive approach to detect later-stage colorectal cancer (CRC); however, they lack the sensitivity to consistently detect early-stage cancers, according to study results published in Clinical Gastroenterology and Hepatology.
The investigators of this study sought to estimate stage-specific sensitivities of quantitative fecal immunochemical tests for detecting CRC in a large cohort of German patients.
Before surgery, the investigators collected stool samples from 435 patients aged 45 to 75 years with newly diagnosed CRC. They calculated stage-specific sensitivities of a quantitative fecal immunochemical test according to manufacturer-recommended cutoff (17 µg/g feces) as well as alternative cutoffs (ranging from 10 to 40 µg/g feces) and applied the sensitivities to different T stages and overall TNM Classification of Malignant Tumors staging; they further stratified stage-specific analyses by tumor location (proximal colon, distal colon, and rectum).
The overall fecal immunochemical test sensitivity was 84.6% (95% CI, 80.9%-87.9%) at the recommended cutoff and ranged from 79.1% (95% CI, 75%-82.8%) at 40 µg/g to 89% (95% CI, 85.6%-91.8%) at 10 µg/g using alternative cutoff values. Over the entire range of cutoffs, the test was notably less sensitive in detecting T1 colorectal cancers and consistently more sensitive in detecting T2 to T4 colorectal cancers.
At the recommended cutoff, the resulting sensitivities for T1, T2, T3, and T4 tumors were 52.2% (95% CI, 36.9%-67.1%; P <.001), 79.2% (95% CI, 68%-87.8%; P <.001), 92.5% (95% CI, 88.6%-95.4%; P <.001), and 83.6% (95% CI, 71.9%-91.8%; P <.001).
According to TNM staging, results using the recommended cutoff were nearly identical in which the sensitivities for stage I, II, III, and IV cancers were 68.2% (95% CI, 57.2%-77.9%; P =.01), 92.3% (95% CI, 86.7%-96.1%; P =.01), 82.2% (95% CI, 73.7%-89%; P =.01), and 89% (95% CI, 80.2%-94.9%; P =.01).
According to tumor location, sensitivities for detecting T1 tumors was particularly low for the distal colon (<40% at all cutoffs).
Limitations to the study were that most cases were recruited in a clinical setting and may not reflect results for screening in the general population. In addition, overall sensitivities at cutoffs between 10 and 20 µg/g were higher than in screening studies.
The investigators determined an overall high sensitivity of the fecal immunochemical test to identify patients with later-stage CRC; however, the test missed one-third of stage I cancers, and future studies should look to improve detection of early-stage CRC.
Niedermaier T, Tikk K, Gies A, Bieck S, Brenner H. Sensitivity of fecal immunochemical test for colorectal cancer detection differs according to stage and location [published online January 24, 2020]. Clin Gasteroenterol Hepatol. doi:10.1016/j.cgh.2020.01.025