Home-Based Stool Test Detects 79% of Colorectal Cancers

Diedtra Henderson

February 04, 2014

The fecal immunochemical test (FIT), a simple at-home stool test that requires no change in diet to complete, can accurately detect 79% of colorectal cancers (CRCs). In addition, 2 of the most well-studied FIT brands are highly sensitive and specific, according to a meta-analysis of 19 studies.

Jeffrey K. Lee, MD, from the University of California, San Francisco, and coauthors published the findings of their evidence review in the February 4 issue of the Annals of Internal Medicine.

CRC is the second leading cause of cancer-related deaths in the United States, after lung cancer, according to the Centers for Disease Control and Prevention (CDC).

Although screening is helpful in preventing cancer, the other at-home test, the fecal occult blood test, only detects 13% to 50% of cancers with a single round of screening, according to Dr. Lee and coauthors. Colonoscopy resources also are limited in some locations, the researchers note. The CDC reports that 1 in 3 adults aged 50 to 75 years (or more than 20 million people) have not been tested for colorectal cancer as recommended by the US Preventive Services Task Force (USPSTF).

A growing number of medical professional societies are advocating for the use of FIT, but precise estimates of the sensitivity of the testing are lacking. The authors reviewed the evidence to gauge how accurate FIT is in diagnosing CRC. They conducted a full-text review of 53 studies, including 9 studies examined by the USPSTF in 2008. Of those, they included 19 articles in their analysis.

The studies had sample sizes ranging from 80 to 27,860 and examined 8 different FIT brands. Twelve of the studies used colonoscopy regardless of FIT results, and 7 studies used colonoscopy only in patients with positive FIT results. The mean patient age ranged from 45.2 to 62.7 years.

FIT "detects 4 in 5 cancers with just a single testing and points to 94% of people who don't have cancer," Elizabeth G. Liles, MD, MCR, a researcher at Kaiser Permanente's Center for Health Research in Portland, Oregon, told Medscape Medical News. FIT remains "a viable option for screening. It has great potential for being accurate. We already know it's a really convenient way to screen and could be accessible to a lot of people."

It remains unclear whether FIT should be the CRC screening test of first resort, with colonoscopy reserved for patients with positive FIT results.

"You would need to directly compare those 2 tests. The studies we looked at didn't ask that question," Dr. Liles said. Two ongoing randomized controlled trials (one [Colonoscopy Versus Fecal Immunochemical Test in Reducing Mortality From Colorectal Cancer (CONFIRM)] being conducted in the United States and the other in Spain) should answer that question within 3 to 5 years, she says. Both trials compare colonoscopy with FIT effectiveness for screening; each is enrolling about 50,000 participants.

Two of the brands included in the current meta-analysis, OC-Micro/Sensor (Eiken Chemical) and OC-Light (Polymedco), had several studies that could be pooled and that demonstrated similar sensitivity and specificity (93% and 91% for OC-Light and 86% and 91% for OC-Micro/Sensor, respectively).

Although patients are more likely to complete FIT because of ease of use, it is unlikely to pare healthcare spending. Kaiser, for instance, uses automatic reminder calls with FIT tests, sends letters (which results in postage and additional costs), and engages support staff to contact patients directly, Dr. Liles said.

"[T]his systematic review and meta-analysis suggests that FITs have high accuracy, high specificity, and moderately high sensitivity for detection of CRC," Dr. Lee and colleagues conclude. "Pooled test performance estimates show that the accuracy of a specific qualitative FIT (OC-Light) is similar to that of a specific quantitative FIT (OC-Micro/Sensor) for detecting CRC. This finding suggests that FIT type could be customized to different-sized care settings without significant variability in accuracy."

Support for this study was provided by the National Institutes of Health, National Cancer Institute, National Institute of Diabetes and Digestive and Kidney Diseases, National Cancer Institute Cancer Research Network, and Population-Based Research Optimizing Screening Through Personalized Regimens. One author disclosed receiving a grant from the National Cancer Institute during the conduct of the study and receiving a grant from Pfizer in the 36 months before publication. The remaining authors have disclosed no relevant financial relationships.

Ann Intern Med. 2014;160:171-181. Abstract

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