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Sponge Cytology As a Novel Screening Tool for the Early Detection of Esophageal Cancer; Pilot Results From the First U.S. Trial
Kelly Haisley*1, Sergio Toledo-Valdovinos1, Gene Bakis2, Brintha K. Enestvedt2, James P. Dolan1, John G. Hunter1
1Surgery, Oregon Health and Science University, Portland, OR; 2Gastroenterology, Oregon Health and Science University, Portland, OR
Background: Despite the increasing prevalence of esophageal cancer (EC), there is currently no cost-effective screening test for the early detection of the disease. While esophageal cytology utilizing retrievable sponges has been examined in other countries, this technique has not been previously studied in the United States (U.S.). Thus, our aim was to assess the feasibility and safety of sponge cytology in a U.S. population. Our secondary goal was to evaluate the reliability of fluorescent in-situ hybridization (FISH) as a method for detecting cellular atypia in tissues obtained by sponge cytology.
Methods: A pilot study was performed at a single, multidisciplinary NCI-designated cancer center. Appropriately selected patients who were scheduled for screening or therapeutic esophagogastroduodenoscopy (EGD) underwent a standardized sponge cytology sampling prior to their procedure in which a small capsule attached to a string is swallowed, dissolving in the stomach to release a 15mm sponge (Figure 1). With gentle traction on the string, the sponge is withdrawn, collecting a sample of esophageal cells. EGD was then performed to determine the pathologic diagnosis as either normal or abnormal (esophagitis, metaplasia/dysplasia, or EC) and to assess for complications related to sponge use. Sponge samples were placed in buffer and sent for blinded FISH analysis to look for loss of the p53 gene, a mutation known to be highly prevalent in esophageal dysplasia and EC.
Results: Fifty patients were enrolled (68% male, 96% Caucasian) with a median age of 67 years. Every patient successfully swallowed the capsule and no complications such as string breakage, bleeding or mucosal injury occurred. Cell collection was very effective with 98% of sponge samples having sufficient yields to perform FISH. Two patients were excluded from final analysis, the first due to failure of the FISH probe and the second due to not completing EGD (for reasons unrelated to the sponge). Ultimately, 48 patients were analyzed with 18 having normal EGDs and 30 having endoscopic abnormalities (3 esophagitis, 24 metaplasia/dysplasia and 3 EC). A total of 5 FISH probes demonstrated p53 loss with these same 5 patients having a high likelihood of an abnormal EGD (94% specificity). Unfortunately, the sensitivity of the FISH probe to detect abnormalities was only 12.5% for any abnormal EGD, 8.3% for metaplasia/dysplasia and 0% for EC itself.
Conclusion: Esophageal sponge cytology is a safe, cost effective and tolerable method for collecting esophageal cell samples. While the esophageal sponge is an extremely promising technique, FISH does not appear to be a reliable method for detecting cancer in these samples. More study is necessary to identify new molecular techniques to utilize with esophageal sponge cytology to improve the utility of this screening modality.
 Figure 1: Oesotest esophageal sponge
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