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June 25, 2020

“Sponge on a String” Test for Barrett’s Esophagus and Esophageal Cancer Continues to Show Promise

By Nicole Ferrara

Mayo Clinic researchers have confirmed the accuracy of a minimally invasive method to detect and help prevent esophageal cancer in patients at risk for Barrett's esophagus and esophageal cancer.  Results of their study have been published in the American Journal of Gastroenterology.

In Barrett's esophagus, tissue in the esophagus is replaced by tissue similar to the intestinal lining. Often diagnosed in people who have long-term gastroesophageal reflux disease (GERD), Barrett's esophagus is associated with an increased risk of developing esophageal cancer, the sixth most common cause of cancer deaths worldwide, according to the American Cancer Society.

Illustration comparing a normal lower esophagus with an esophagus that has developed Barrett's esophagus.

“The challenge with the most common type of esophageal cancer in the West, adenocarcinoma, is that 80 to 90 percent of cases come to us at an advanced stage,” says Prasad Iyer, M.D., a gastroenterologist at Mayo Clinic in Rochester, Minnesota.  “These patients can’t swallow. When esophageal cancer is diagnosed at that point, only about 20 percent of patients survive five years.”

If esophageal cancer is found early, the survival rate is much higher. “If you diagnose this cancer before the onset of symptoms, survival is 80 or 90 percent,” says Dr. Iyer. “Early detection is a real opportunity to save lives.”

The only symptom of Barrett’s esophagus is reflux, and while patients with reflux often take medication to relieve symptoms, they are rarely tested for Barrett’s esophagus or esophageal cancer. These conditions are currently diagnosed using an endoscope, which involves an invasive, expensive procedure that requires sedation.

Dr. Iyer and his team developed a method to diagnose Barrett's esophagus and esophageal cancer using a compressed sponge on a string inside a capsule covered with a dissolvable shell. A patient undergoing the test swallows the capsule with a few sips of water. Within eight minutes the capsule dissolves, releasing the sponge, which is then pulled out using the attached string. The sponge provides cell samples of the entire esophagus, which are then tested for biomarkers consistent with cancer or precancer.

Photograph of Prasad Iyer, M.D.
Prasad Iyer, M.D.

In this new study, 268 participants swallowed the sponge capsule and the expanded sponge was removed with the attached cord eight minutes later. Patients then underwent endoscopy within 24 hours. The sponge on a string was well-tolerated – 95% of participants preferred it to endoscopy. And the five biomarkers used in the sponge test accurately identified 92% of Barrett’s esophagus or esophageal cancer cases, while correctly determining no presence of precancer or cancer 94% of the time.

Patients were recruited for the study at Mayo Clinic’s campuses in Rochester, Minnesota, and Jacksonville, Florida and at Mayo Clinic Health System in Austin, Minnesota. The sponge test was administered by both physicians and nurses, with comparable success rates.

“The whole procedure takes about 10 minutes, doesn’t require sedation, will be substantially less expensive than endoscopy and can be completed by a nurse in in a primary care office,” says Dr. Iyer.

The research team initially documented the discovery and validation of novel methylated markers along with results of a pilot study in the American Journal of Gastroenterology in 2018. Dr. Iyer and his colleagues used the data they compiled from these two studies to obtain a grant from the National Cancer Institute to conduct a trial with 1,500 participants in the Mayo Clinic Health System. John Kisiel, M.D., also a gastroenterologist at Mayo Clinic in Rochester, Minnesota, will partner with Dr. Iyer on this grant. Drs. Iyer and Kisiel are developing biomarker assays for the trial in collaboration with Exact Sciences.

Photograph of John Kisiel, M.D.
John Kisiel, M.D.

“We are making great progress in developing a minimally invasive tool to detect esophageal cancer and its precursor early,” says Dr. Iyer. ”This test has the potential to dramatically alter the accessibility, cost and feasibility of testing.”

An abstract on this study was also accepted for Digestive Disease Week 2020: “Independent Validation of an Accurate Methylated DNA Marker Panel for the Non-endoscopic Detection of Barrett’s Esophagus: A Multisite Case Control Study.”

This study was partially supported by grants from the National Cancer Institute (CA214679 to JBK and CA241164 to PGI and JBK). Materials, reagents and blinded TELQAS assays were provided by Exact Sciences.

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Tags: Barrett's esophagus, biomarkers, cancer, cancer screening, esophageal cancer, gastroenterology, gastrointestinal cancer, John Kisiel, Mayo Clinic Cancer Center, Mayo Clinic Health System, National Cancer Institute, News, Prasad Iyer

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