SAN DIEGO – A quick, inexpensive, and well-tolerated sponge-on-a-string esophageal biopsy, combined with methylated DNA analysis, discriminated Barrett’s esophagus from normal tissue with perfect accuracy in a pilot study at the Mayo Clinic in Rochester, Minn.
The investigators used tissue samples from over 100 patients to identify methylated DNA markers that discriminated Barrett’s esophagitis from healthy tissue with an area under the curve (AUC) of more than 0.9. They then had 19 patients with endoscopically confirmed Barrett’s and 20 controls who had Barrett’s ruled out on previous endoscopies swallow a polyurethane foam sponge that expanded to 25 mm after its surrounding gelatin capsule dissolved.
Dr. Prasad G. Iyer
After 10 minutes, the sponge was pulled out by its cord. Methylation-specific polymerase chain reaction (PCR) testing was performed on DNA extracted from the sponge. The results were checked against follow-up endoscopies in the 39 subjects.
When taken together, two DNA markers – methylation of the vav guanine nucleotide exchange factor 3 (VAV3) and zinc finger protein 682 (ZNF682) genes – were 100% specific and 100% sensitive for Barrett’s esophagus, with an AUC of 1.0.
“We achieved perfect discrimination between Barrett’s and non-Barrett’s tissue. We are at the threshold of developing an accurate, minimally invasive tool for Barrett’s and Barrett’s dysplasia screening,” said lead investigator Prasad G. Iyer, M.D., a gastroenterology professor at Mayo.
His team didn’t use the Cytosponge, which is being developed for similar purposes and has been in the medical news lately. Instead, they used the EsophaCap from Capnostics, which was approved by the Food and Drug Administration in the 1990s.
“This technique would allow us to take” Barrett’s screening out of “the GI lab and into a primary care office, where it can be performed by a nurse or even a technician, without the expense and side effects of endoscopy” he said. After the sponge is retrieved, staff would just have to process it a bit and send it off for methylation-specific PCR. The ease and accuracy could increase screening: “That’s where I think a tool like this” – which might cost $200 – “could substitute for endoscopy, which costs a couple thousand.” Endoscopies could be limited to patients who are sponge-positive for Barrett’s, Dr. Iyer said at the annual Digestive Disease Week.
“Our next goal is to identify markers which will tell us who amongst those with Barrett’s have dysplasia. At this point in time, we are doing” endoscopic surveillance for dysplasia and early cancer, Dr. Iyer said, and the sponge-and-marker approach might have significant advantages. A prospective trial is in the works with almost 250 patients.
Barrett’s patients were a median of 66 years old, their lesion lengths were 4-7.5 cm, and about 80% were men. Half had no dysplasia, and about a quarter each had low-grade dysplasia and high-grade disease/esophageal adenocarcinoma. The controls were somewhat younger, with a median age of 61 years, and half were men.
The study was funded by Exact Science, which performed the methylated DNA analysis. Dr. Iyer and other investigators are involved with the company, and the Mayo Clinic is an equity investor.