CHICAGO, June 4 — It may be feasible to screen for all cancers of the gastrointestinal tract with a stool DNA test, a researcher said here.

• Explain to interested patients that the researcher said any stool DNA test for screening all GI cancers is likely about five years away.
• Note that this study was published as an abstract and presented as a poster at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Such a test detected mutations from the tumors of 68% of patients who had known GI cancers, located from the oropharynx to the colon, David Ahlquist, M.D., of the Mayo Clinic in Rochester, Minn., reported at Digestive Disease Week.

There were no false-positives in a control group of patients who were free from GI symptoms and had a normal colonoscopy.

Dr. Ahlquist said he and his colleagues went into the study with the expectation that a 50% detection rate would be a success.

“So we’re very encouraged by this as a feasible approach to screening multiple cancers with a single test,” he said.

The technology already exists to screen for colon cancer with a stool DNA test, he said, but other GI cancers account for twice as many deaths and are not currently screened for.

Because high cure rates can be achieved when these cancers are discovered in the early, presymptomatic stages, reliable screening is a priority, he said.

To assess the feasibility of a stool DNA test for all GI cancers, Dr. Ahlquist and his colleagues collected samples from 70 patients with proven GI cancers and 70 healthy controls matched by age and sex (median age 65; 65% male).

They identified mutations in tissue biopsies to serve as markers for each patient’s tumor and searched for the mutations in the stool of the patients and a matched control.

The mutations showed up in 68% of the stool samples from the patients with cancer and none of the control samples.

Broken down by type, the test identified 40% of oropharyngeal, 65% of esophageal, 62% of pancreatic, 75% of biliary/gall bladder, and 100% of stomach and colorectal cancers.

The test also identified 61% of the patients with precancers — 100% of pancreatic intraductular papillary mucinous neoplasia and 56% of colorectal advanced adenoma.

Although the initial results are promising and establish the feasibility of the test, Dr. Ahlquist acknowledged that it would probably take five years to develop a product.

“There’s a lot more work that needs to be done,” he said. “Additional clinical studies need to be done to validate this, to optimize it, and eventually to take it into a multicenter study.”

He envisioned the final test as one that would be used to screen the general population for these cancers.

“If you wait for symptoms for most of these cancers, they’re already late stage,” he said. “So if we’re going to improve outcomes in these patients, it’s going to require intervening with a screening test before symptoms occur, and that’s targeting the population.”

The study was supported by a grant from Charles Oswald Foundation. The study authors have issued and filed patents covering methods used in this study.

Primary source: Digestive Disease Week

Source reference:
Zou H, et al “Pan-detection of gastrointestinal neoplasms by stool DNA test: establishment of feasibility” DDW 2009; Abstract T2036.

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