Fecal Immunochemical Testing

Earlier CRC screening with colonoscopy, FIT cost-effective ‘irrespective of BMI’

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Regardless of patient sex or BMI, initiating colorectal cancer screening with colonoscopy at age 45 years or with fecal immunochemical testing at age 40 years was cost-effective, according to new research.

In addition, researchers reported CRC screening with colonoscopy at age 40 years was cost-effective in men with class 2 and 3 obesity, whom investigators noted have the highest risk for CRC and all-cause mortality.

study data

“Initiating CRC colonoscopy-based screening at age 45 years is likely to be cost-effective for women and men irrespective of BMI, initiating colonoscopy-based screening at age 40 years may be cost-effective in men with obesity [class 2 to 3], and FIT-based screening may be cost-effective starting at age 40 years in both sexes across the range of BMI,” Aaron Yeoh, MD, and colleagues from the division of gastroenterology and hepatology at Stanford University School of Medicine, wrote in Clinical Gastroenterology and Hepatology.

As obesity is a suspected risk factor for CRC, researchers sought to determine whether intensified CRC screening would be cost-effective in overweight and obese individuals, noting that obesity also is associated with increased morbidity and mortality risks and incremental costs. “Given these competing risks, our aim was to estimate the potential clinical impact and cost-effectiveness of earlier initiation or more intensive CRC screening in overweight and obese persons,” they wrote.

Using a decision analytic model that was recalibrated to avoid double-counting the impact of BMI and birth cohort effect of increasing CRC incidence at younger ages, investigators compared CRC screening initiated at ages 45 or 40 years vs. 50 years in men and women with BMI that ranged from normal weight to class 3 obesity.

They analyzed 10 cohorts, grouped by age and BMI, and studied the impact of annual fecal immunochemical testing (FIT) and colonoscopy every 5 and 10 years. Incremental costs and quality of life-years (QALY) gained were calculated using a payer perspective, with cost-effectiveness defined as no more than $100,000/QALY gained.

Without CRC screening, investigators reported comparable sex-specific total CRC mortality for individuals who were overweight or had class 1 to 3 obesity, “reflecting the counterbalancing of higher CRC risk by lower life expectancy as BMI rises.”

Across BMI categories and sex groups, initiating colonoscopy at age 45 vs. 50 years with routine screening every 10 years through age 75 years cost $33,400 to $85,900/QALY gained. However, researchers reported starting screening at age 40 vs. 45 years with subsequent colonoscopies at 10-year intervals was only cost-effective for men with class 2 or 3 obesity ($93,300/QALY gained vs. $80,400/QALY gained, respectively). In addition, starting FIT at age 40 vs. 45 years cost $22,000/QALY to $58,800/QALY gained for both sexes and across BMI groups.

“Our finding that initiating CRC screening at age 45 years appears cost-effective across

the range of BMI groups, and that even earlier initiation at age 40 years appears cost-effective in men with obesity [class 2 to 3], suggests that the benefits of earlier CRC screening are substantial even when the higher CRC risks in overweight and obese persons are balanced against the higher risk of competing morbidity and mortality, and overweight- and obesity-associated costs that are incurred when CRC death is averted,” researchers wrote. “These findings have implications for CRC screening in overweight and obese persons specifically, and for risk-adjusted CRC screening more generally.”

Fecal Immunochemical Testing for Colorectal Cancer Screening.

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FIT detected most cancers, but only a minority of advanced adenomas.

Fecal immunochemical testing (FIT) might be more accurate than guaiac-based fecal occult blood testing (gFOBT) in screening for colorectal cancer. In this Dutch study, 1256 average-risk patients submitted single specimens for FIT (OC-Sensor) just before undergoing screening colonoscopy.

Colonoscopy identified 8 patients (0.6%) with colorectal cancer and 113 (9%) with advanced adenomas. At a cutoff of 50 ng/mL, FIT was positive in 10% of patients. Sensitivity and specificity of FIT for detecting advanced adenomas were 38% and 93%, respectively. For colorectal carcinoma, sensitivity was 88% (i.e., FIT was positive in 7 of 8 patients with cancer), and specificity was 91%. Five of the seven FIT-positive cancers were localized (Dukes stage A). FIT detected proximal and distal advanced neoplasia with equal sensitivity.

The Journal Watch General Medicine Perspective

According to these findings, if patients were screened initially with a single FIT, most localized cancers and about one third of advanced adenomas would be detected, and 90% of patients (those who were FIT-negative) would avoid colonoscopy. Failure to detect most advanced adenomas is not necessarily a fatal flaw, if additional research shows that repeated FIT screening (i.e., at 1- or 2-year intervals) detects many of these lesions before they progress to unresectable cancers. One of our Journal Watch Gastroenterology editors, an expert in colorectal cancer screening, comments below on FIT.

The Journal Watch Gastroenterology Perspective

Current colorectal cancer screening guidelines recommend that clinicians who use fecal blood testing switch from gFOBT to FIT (Am J Gastroenterol 2009; 104:739). Consistent results from several types of studies, including randomized, controlled trials, indicate that patient adherence (i.e., completion of the test) and test sensitivity strongly favor FIT over gFOBT. Several national screening programs outside the U.S. now are based on FIT, and cost-effectiveness analyses suggest that annual FIT is at least as cost-effective as is colonoscopy every 10 years. Several randomized, controlled trials, including one in U.S. Veterans Administration hospitals) have been organized to compare FIT and colonoscopy.

A practical problem that clinicians encounter when they try to switch to FIT is the lack of comparative performance data on the several commercial FIT assays available in the U.S. Several years ago, in a study of six commercial FITs available in Germany, researchers found that several had awful performance characteristics, including very poor specificity. However, the laboratory-based assay used in the current study (OC-Sensor) has been evaluated in many studies and is believed to perform best.

This Dutch study suggests that FIT is equally effective in both the proximal and distal colon, whereas some previous evidence had suggested better performance in the distal colon. This result is encouraging, but the endpoint for the study was advanced conventional (i.e., tubular, tubulovillous, or villous) adenomas. The study ignores (as do all FIT studies) the 30% of colorectal cancers that arise through a genetic pathway characterized by hypermethylation; the precursors of these cancers are not conventional adenomas but rather serrated lesions (sessile serrated polyps, also known as sessile serrated adenomas). Further, these serrated lesions are located primarily in the proximal colon. Endoscopically, these premalignant serrated lesions have no vessels on their surface, and some evidence shows that they don’t bleed at all. The future of sensitive fecal testing that can identify both conventional and serrated precancerous lesions in the proximal colon is more likely to lie in fecal DNA testing than in FIT.

Source: Journal Watch General Medicine