Studies on the CEA-like substance in gastric juice

An endogastric capsule for measuring tumor markers in gastric juice: an evaluation of the safety and efficacy of a new diagnostic tool

BACKGROUND

In gastric juice, high levels of the carcinoembryonic antigen (CEA) and the carbohydrate antigen 19-9 (CA 19-9) have been found to correlate with precancerous lesions and gastric cancer. So far, sampling of gastric juice has required upper endoscopy. In place of this invasive procedure, we investigated a new tool for the quantitation of tumor markers in gastric juice.

MATERIALS AND METHODS

The study population consisted of healthy controls and consecutive subjects with suspected gastric cancer or dyspepsia/epigastric distress. Patients were asked to swallow a small gelatine capsule (14 mm in length and 5 mm in diameter) containing a pierced plastic cover and surrounding a piece of absorbent paper. The capsule was left in the gastric cavity for 60 min to allow saturation of the absorbent paper with gastric juice. A 45-50 cm length of nylon thread connected to the inner capsule was used to remove the device from the gastric cavity. After processing the absorbent paper for radioimmunoassay, CEA and CA 19-9 levels were correlated to the findings of upper endoscopy and biopsies of gastric mucosa or suspected lesions.

RESULTS

The endogastric capsule did not cause any side-effects and 62 participants were fully compliant to the procedure. Assessable gastric juice samples were taken from 23 patients with gastric cancer, 15 patients with intestinal metaplasia or dysplasia, 12 patients with gastritis and 12 controls without gastric diseases. In the 12 samples of gastric juice from control patients, mean values of CEA and CA 19-9 were 1.1 +/- 0.9 ng/ml and 16 +/- 7.5 ng/ml, respectively. The mean levels of both markers were found to increase according to the severity of gastric lesions and in patients with cancer, mean CEA and CA 19-9 levels were 513 +/- 627 ng/ml and 545 +/- 510 ng/ml, respectively. Patients with precancerous lesions and cancer showed higher levels of CEA and CA 19-9 than patients with normal findings or gastritis (P <0.001).

CONCLUSIONS

The endogastric capsule is a simple, non-invasive tool for the measurement of CEA and CA 19-9 levels in gastric juice. These values may discriminate between normal or minor pathologic changes and precancerous lesions or carcinomas. Further investigations are warranted, since this may represent a new method for gastric cancer screening.

Tumor marker radioimmunoassays in gastric juice. Methodologic drawbacks due to pH variations

Conflicting data have been reported on tumor marker determination in gastric juice. In the present study the effect of pH variations on both antibody-antigen binding and the immunologic stability of the antigen were evaluated for the radioimmunoassay of carcinoembryonic antigen, CA19-9, tissue polypeptide antigen, and ferritin. A significant inhibition of antibody-antigen binding was constantly found in acidic conditions. Antigen concentration was lower in acidified than in untreated samples, possibly due to the carryover of acidity in the incubation mixture. Neutralization of acidified samples partly improved recovery of carcinoembryonic antigen and CA19-9. Tissue polypeptide antigen and ferritin were not recovered by neutralization in samples with pH less than 4.5, suggesting an irreversible damage of the immunologic characteristics of the two antigens. From the present data we conclude that an accurate validation of methods and a rigorous standardization of sample collection are mandatory for tumor marker determination by radioimmunoassay in gastric juice.

Carcinoembryonic antigen in gastric juice collected during endoscopy. Value in detecting high-risk patients and gastric cancer

In order to ascertain the role of gastric carcinoembryonic antigen (CEA) determination in detecting patients with a risk for gastric cancer, 69 subjects were studied; 23 were referred for endoscopy because of dyspepsia but without obvious macroscopic lesions, 27 with duodenal ulcer, 11 with benign gastric ulcer, 8 with gastric cancer. The following results were obtained by subdividing the material according to the histologic interpretation of the results of gastric mucosal biopsies: (1) in the presence of minor histologic abnormalities of the gastric mucosa, CEA in gastric juice was under 100 ng/ml in all but five cases; and (2) in moderate or severe chronic atrophic gastritis (associated or otherwise with intestinal metaplasia or dysplasia), and in gastric cancer, gastric CEA ranged between 224 and 3120 ng/ml in all but two cases. Although not diagnostic for gastric cancer, gastric CEA is a promising test in detecting patients at risk, including those with dysplasia of the gastric mucosa.