Fecal immunochemical test accurate for cancer in patients at high risk

Reuters Health Information: Fecal immunochemical test accurate for cancer in patients at high risk

Fecal immunochemical test accurate for cancer in patients at high risk

Last Updated: 2017-06-20

By Will Boggs MD

NEW YORK (Reuters Health) - The fecal immunochemical test (FIT) has high diagnostic accuracy for colorectal cancer (CRC) in patients at increased risk, according to a meta-analysis.

It’s less accurate, however, at diagnosing advanced neoplasia (AN) in these patients.

“International organizations recommend colonoscopy as the most effective screening method for subjects at increased risk for colorectal cancer,” Dr. Anastasia Katsoula from Aristotle University of Thessaloniki, Greece told Reuters Health by email. “Our research supports the use of fecal immunochemical testing as an alternative non-interventional screening strategy for subjects at increased personal or familial risk who refuse to use colonoscopy.”

“Moreover,” she said, “offering multiple screening options means screening can be tailored to individual preferences and values, hence enabling a patient-centered approach.”

The high accuracy and adherence associated with FIT recommend its use for population-based screening, but its role in screening individuals at increased risk for CRC has been unclear.

In a systematic review and meta-analysis of 11 cross-sectional studies and one randomized clinical trial, Dr. Katsoula and colleagues explored the diagnostic accuracy of FIT for CRC or AN in asymptomatic individuals with a familial or personal history of CRC.

FIT sensitivity and specificity for diagnosing CRC ranged from 25% to 100% (median, 81%) and from 87% to 95% (median, 91%), respectively. For diagnosing AN, sensitivity and specificity ranged from 29% to 83% (median, 50%) and from 85% to 98% (median, 92%), respectively.

For CRC, pooled estimates of sensitivity and specificity were 93% and 91%, respectively, with 7.7% positive predictive value and 99.9% negative predictive value, according to the June 19th JAMA Internal Medicine online report.

For AN, pooled estimates of sensitivity and specificity were 48% and 93%, respectively, with 43.8% positive predictive value and 94.0% negative predictive value.

Overall diagnostic accuracy (using ROC AUC) was 93% for CRC and 86% for AN.

“A series of subgroup, sensitivity, and meta-regression analyses verified robustness of our conclusions, despite a high degree of heterogeneity and wide confidence intervals of the pooled estimates,” Dr. Katsoula said.

“Use of cutoff values between 15 to 25 mcg Hb/g feces offers the best combination of sensitivity and specificity for diagnosis of CRC or AN,” she said.

“Based on our results, physicians have now an alternative screening option for individuals at increased personal or familial risk,” she said. “They can suggest FIT as an alternative screening strategy to patients who refuse to undergo colonoscopy. Patients with positive results will be referred for colonoscopy. On the other hand, subjects with negative FIT results should be fully informed that a negative test does not eliminate the possibility of colorectal cancer and about the importance of repeated stool testing.”

“Further research needs to clarify the impact of FIT on quality of life, morbidity, mortality, and its overall cost-effectiveness,” Dr. Katsoula added. “Moreover, new studies are needed to establish optimal thresholds and number of FIT samples and to evaluate the interval time that patients at increased risk should repeat the fecal immunochemical testing.”

Dr. Grigorios I. Leontiadis from McMaster University, Hamilton, Ontario, Canada, who wrote an editorial related to this report, told Reuters Health by email, “If we accept the diagnostic accuracy results of FIT in high-risk patients as shown, then FIT should have very limited role in these patients, given its unacceptably low sensitivity for noncancerous advance neoplasia. Such patients should receive the gold-standard test, which is colonoscopy.”

“However, the trustworthiness of the evidence is so low, that future, better designed and better conducted studies may prove that we were completely wrong in our assessment of the diagnostic accuracy of FIT: it may be shown to be much better or much worse that what this systematic review has found,” he said. “Therefore, the case should not be closed; further, better research is needed.”

“Until we have better data, FIT could be used (instead of direct assessment with colonoscopy) in high-risk patients in special situations: for example, in individuals who are not willing to have a colonoscopy unless FIT is positive; individuals with comorbidities that render colonoscopy more challenging or risky than usual; individuals who are only interested in secondary prevention of colorectal cancer (diagnosis and treatment of early, asymptomatic cancer) and not in primary prevention (diagnosis and resection of colonic adenomas),” he said.

“I want to make it clear that the authors of this systematic review and meta-analysis did an outstanding job,” Dr. Leontiadis added. “The paper could not reach a definitive conclusion not because these authors did something wrong, but because of the limitations and characteristics of the available data.”

SOURCE: http://bit.ly/2rAuRFW

JAMA Intern Med 2017.

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