Stool DNA Test Too Expensive for Medicare Use, Says Study

Nick Mulcahy

September 20, 2010

September 20, 2010 — Stool DNA testing is currently too expensive to be reimbursed by Medicare for colorectal cancer screening, according to a new modeling study funded by the federal government.

However, the conclusion of the study, which appears in the September 20 issue of the Annals of Internal Medicine, is open to change, suggest the authors.

"Stool DNA testing could be a cost-effective alternative for colorectal cancer screening if the cost of the test substantially decreased," write the authors, led by Iris Lansdorp-Vogelaar, PhD, from the Erasmus Medical Center, Rotterdam, the Netherlands.

The test would have to drop in price from about $350, the current cost, to about $50 per test, say the authors.

The authors also found that stool DNA testing — at its current $350 cost — would be a viable tool if "its availability would entice a large fraction of otherwise unscreened persons to receive screening," they write. Specifically, the "relative adherence" to stool DNA testing would have to be "at least 50% better than that with other screening tests."

Dr. Lansdorp-Vogelaar collaborated with American academics on the study, which was funded by the Agency for Healthcare Research and Quality (AHRQ) and the National Cancer Institute.

The authors note that their findings and conclusions do not necessarily represent the views of the AHRQ.

The purpose of the study was to evaluate the conditions under which stool DNA testing could be cost-effective, compared with the colorectal cancer screening tests currently reimbursed by the Centers for Medicare & Medicaid Services.

Stool DNA vs All the Other Tests

In the analysis, a stool DNA test was scheduled every 3 or 5 years; the results were compared with those from currently recommended colorectal cancer screening strategies, including an annual fecal occult blood test (FOBT) and a colonoscopy every 10 years.

As a screening tool, stool DNA testing has obvious advantages over colonoscopy and sigmoidoscopy in terms of patient comfort. But it is more akin, practically, to another screening stool test — the relatively inexpensive FOBT.

A colorectal cancer screening expert who was not involved in the study explained how the 2 tests differ.

"The FOBT can detect occult blood in the stool, and this serves as a marker for colon cancer because most tumors will intermittently bleed. In contrast, stool DNA tests are designed to detect specific mutations in colon cancer cells that are sloughed off and become mixed into stool," said Daniel C. Chung, MD, director of the High-Risk GI Cancer Clinic at Massachusetts General Hospital in Boston.

Patients who have a positive FOBT or stool DNA test must then have a colonoscopy, he added.

Stool DNA testing has "several potential advantages" over FOBT, Dr. Chung told Medscape Medical News.

"It is an assay directed specifically at tumor cells and not at an indirect marker like blood. This would theoretically make it more likely to pick up tumors," he explained.

However, in the new study, the authors, who used published data in their projections, indicated that the sensitivity of immunochemical FOBT and stool DNA (based on PreGen-Plus, version 1.1) for detecting colorectal cancers was the same: 70%.

But Dr. Chung highlighted the stool DNA's superiority in detecting precancerous polyps.

"Another potential advantage is that it may detect precancerous polyps better than FOBT because polyps harbor some of the same mutations and polyps may be less likely to bleed,' he said.

Indeed, in the study, the authors indicated that, according to published literature, stool DNA is more sensitive in this regard, especially for larger polyps.

Nevertheless, the study authors found that stool DNA testing, at both 3- and 5-year testing intervals, was "more costly and less effective than annual screening with a sensitive FOBT."

Dr. Chung suggested that there is hope for stool DNA testing: "Stool DNA tests are continuing to evolve, so the performance characteristics and costs of future generations of these tests may become more competitive."

Modeling Study Details

Using previously published data on stool DNA, FOBT, and the other screening modalities, the authors performed a comparative "microsimulation modeling study using 2 independently developed models."

Each model simulates the life histories of a large population of people from birth to death and has a natural history component that tracks the progression of underlying colorectal disease in the absence of screening, write the authors.

The natural history models use all-cause mortality estimates from American life tables and colorectal cancer survival data from the Surveillance, Epidemiology, and End-Results (SEER) Program (1996 to 1999).

The target population in the study was 65 years of age. The authors also did a sensitivity analysis for a target population 50 years of age and report that none of the results changed substantially when this younger cohort was considered.

The authors have disclosed no relevant financial relationships.

Ann Intern Med. 2010;153:368-377.