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Endoscopic ultrasound aids cancer assessment: esophageal, pancreatic.

BOSTON -- When CT scans and endoscopic retrograde cholangiopancreatography are inconclusive, endoscopic ultrasound can be useful in the diagnosis and staging of esophageal and pancreatic cancer.

Endoscopic ultrasound (EUS) is the most accurate method for assessing the size and depth of local esophageal tumors and local involvement of lymph nodes, and the technology can help physicians diagnose and drain cystic lesions of the pancreas, Dr. Brian Jacobson said at a symposium on treating gastrointestinal disorders sponsored by Boston University.

Although it is less accurate than other methods in finding metastases, EUS has a range of ontology applications. These include staging of esophageal cancer, fine needle aspiration of mediastinal adenopathy, evaluation of subepithelial masses (or submucosal lesions), diagnosing and staging of pancreatobiliary tumors, and staging of rectal cancer, said Dr. Jacobson, associate director of endoscopy at Boston Medical Center.

"Accurate staging of esophageal cancer is very important, not only for prognostic in formation but also for determining the types of treatment the patient should receive," he said. "And there are studies that show accurate staging is actually cost effective."

But staging of esophageal cancer can be difficult because of the need for precise imaging. "For all stages of esophageal cancer. EUS is far superior" to CT scans, with accuracy "in the range of 90%," Dr. Jacobson said. He cited published data showing that CT scan accuracy ranged from 29% of T1/T2 tumors--compared with 83%-92% using EUS--and rose no higher than 71% for T3 ("Gastrointestinal Endosonography," J. Van Dam and M.V. Sivak, eds., W.B. Saunders, 1999, p. 142). EUS also can bring nodal staging accuracy to almost 100% with fine-needle aspiration, he added.

He offered a caveat, however, about using EUS to stage tumors after treatment. "We cannot distinguish between fibrosis and scarring or inflammation," Dr. Jacobson said.

One important EUS application could be to second-guess noninvasive imaging of minors that appear to be resectable. "EUS can help confirm that or might be able to show that it actually is not resectable," Dr. Jacobson said, adding that EUS is only 60%-70% accurate in identifying vascular involvement. "If those studies suggest vascular involvement and EUS corroborates that, it is highly predictive of vascular involvement."

When pancreatic pseudocysts show up as lesions on CT scans, EUS can help identify them. "And EUS is useful not only for diagnosis but also for those occasions when we want to drain the pseudocyst," he said.

Dr. Jacobson described three types of EUS instruments:

* The radial endoscope. The tip of this device has ultrasound chips that spin 360 degrees for cross sectional imaging. "The layers of the G1 lumen can be split and seen as distinct entities" using this device, he said.

* The linear echoendoscope. This has no moving parts, but a curved linear array of ultrasound chips. It is used in fine-needle aspiration, so some manufacturers sandblast their needles to make them show up better on ultrasound. "You can follow a needle and guide it into whatever you want to be able to take a biopsy," he said. "And this is what makes EUS such a powerful tool."

* High-frequency probes. Higher frequency results in greater detail but less penetration. Dr. Jacobson recommended a frequency of 20 MHz for evaluating early-stage tumors in the wall of the GI tract, but only 5-7'A MHz for examining the pancreas and surrounding structures.
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Title Annotation:Gastroenterology
Author:Macneil, Jane Salodof
Publication:Internal Medicine News
Date:Jan 1, 2004
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