Is there a use of endoscopic ultrasonography in the follow-up of patients to detect early recurrences after treatment?
R. Lambert (Lyons)
The diagnosis of malignancy in Barrett's esophagus (BE) is made at endoscopy; the forceps biopsies classify the lesion as high grade dysplasia or confirmed cancer. Endoscopic sonography is required for the classification of the neoplastic area at an "early stage"; this occurs when the hyperechoic layer corresponding to the submucosa is intact. The eradication of the lesion is performed either by the surgeon (esophagectomy), or by the endoscopist (local tumorectomy). In the latter condition the esophagus remains in place, with columnar metaplasia or a mucosal lining reversed to the squamous type. It has been proposed to use sonography during the endoscopic procedure as a control of the distance between mucosa and muscularis after saline injection, during strip resection
Endoscopic sonography in the follow up is proposed in complement to endoscopic viewing and CT scan [1-5]. Its role differs in the two treatment modalities. However they share some common requirements:
1) endoscopic sonography is a staging rather than a diagnostic procedure;
2) images during the follow up must be compared to an early post-interventional image rather than to the initial image. Surgery, radiation, even endoscopic procedures, alter significantly the 5 layers diagram of the esophageal wall;
3) conventional sonography at 7.5/12 MHz is required to explore the mediastinal recurrences.
In operated patients, recurrences are detected lately when endoscopy and CT scan are the sole explorations. Indeed the anastomotic recurrence usually begins in the depth of the digestive wall, without altering the mucosal surface. A systematic echoendoscopic surveillance may be of benefit to some patients when a silent recurrence of small volume is detected early enough to be treated curatively by surgery.
Recurrences in patients treated by interventional endoscopy may also escape endoscopic detection when there is a malignant nodal involvement in the mediastinum. However, in most cases the recurrence occurs in the superficial layer of the mucosa; this corresponds to an incomplete destruction or to an actual recurrence. The interventional procedure has been a strip resection, thermal laser, photodynamic therapy. In these patients the follow up is based upon repeated endoscopies plus biopsies. Endoscopic sonography is performed with the sole purpose of staging and thin high frequency probes may be useful.
In conclusion, there is room for endoscopic sonography after treatment of malignancy in the columnar lined esophagus. The conventional echoendoscope exploring the esophageal wall and the mediastinum is the usual instrument. An early postoperative exploration is required as a base for the interpretation of late controls.