1 Department of Histopathology, Azienda Ospedale S. Salvatore, Pesaro; 2 Medical Oncology Unit, Hospital of Urbino; 3 Laboratory of Radioimmunology, Azienda Ospedale S.Salvatore, Pesaro; 4 Institute of Biostatistics, Centro Nazionale delle Ricerche (CNR), Rome, Italy
Received 2 April 2002; revised 13 June 2002; accepted 17 July 2002
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Abstract |
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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 4550 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.
Key words: endogastric capsule, gastric cancer, screening, tumor markers, upper endoscopy
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Introduction |
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Thus far, the sampling of gastric juice for CEA and CA 19-9 determinations has been performed during upper endoscopy [322], and the invasiveness and costs of this procedure have represented major limitations for further analyses in large studies and new developments in this field [23].
More recently, an analysis of CEA levels in absorbent paper disks applied to the nipple has shown significantly higher values in cancerous compared with non-cancerous breasts [24]. This study suggested to us the possibility of an easy and non-invasive diagnostic tool for detecting tumor marker levels in gastric juice.
We hypothesized that sampling of gastric juice could be performed using absorbent paper and that samples could be assessed by radioimmunoassay. An endogastric capsule was designed for this purpose and it was tested for determining CEA and CA 19-9 levels in gastric juice. These measurements were correlated with the findings of upper endoscopy plus multiple biopsies of gastric mucosa.
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Materials and methods |
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In each case, standardized upper endoscopy plus multiple biopsies (4 biopsies for a 95% likelihood of a positive yield for gastric carcinoma) were carried out [25]. Two pathologists reviewed each biopsy and the histological findings were classified into the following categories: normal or unspecific changes of gastric mucosa; simple gastritis; chronic gastritis; atrophic gastritis with or without intestinal metaplasia; dysplasia and gastric carcinoma. Intestinal metaplasia and dysplasia were considered to be precancerous lesions [26, 27].
One week after endoscopy, all patients underwent a concomitant double assessment of CEA and CA 19-9 levels in serum and gastric juice. The determinations of the tumor markers in gastric juices were performed by the endogastric capsule. Different investigators performed these procedures, so that the study could be performed in a blind fashion. Enrolled patients gave their informed consent before study entry.
Endogastric capsule and processing of samples
The endogastric capsule was conceived by one of the investigators (P.M.) and was made by Quercetti, Turin, Italy. It is composed by three main components, which are illustrated in Figure 1. The external envelope is made of gelatine material and it measures 14 mm in length and 5 mm in diameter. The inner capsule is made of plastic inert material and it measures 13 mm in length and 4 mm in diameter. The inner capsule is pierced with three holes and contains a rolled-up piece of absorbent paper. A thin nylon thread, 4550 cm in length, is connected to the cover of the inner endogastric capsule, and is fitted with a small button at the opposite extremity, to be kept between two adjacent teeth.
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Once removed from the inner capsule, the absorbent paper was unrolled and immersed in 1 ml of saline solution. It was agitated for 60 min and then mixed with 0.2 M sodium acetate buffer to neutralize the samples [19, 28]. Subsequently, 0.1 ml of each sample was used for CEA and CA 19-9 radioimmunoassay measurements, using commercially available kits (Abbott Diagnostic Kits; Rome, Italy).
In addition to the planned analysis of the two tumor markers, a preliminary evaluation of Helicobacter pylori (HP) infection was attempted in ten consecutive samples of gastric juice. In these cases, 0.1 ml of the solution was dispersed in bacteriologic capsules with selected culture for HP, and 0.1 ml was analyzed by polymerase chain reaction (PCR).
Statistical analysis
In this study, values were reported as means ± the standard deviation (SD). The effect of treatment was assessed by comparing the different concentrations of CEA and CA19-9 between groups. Two separate analyses of variance were conducted, one for each marker, including a between factor (disease at four levels). Orthogonal contrasts were employed to determine differences among specific means (SPSS software package, version 9.0 for Windows; Chicago, IL). Values of P <0.05 were considered statistically significant.
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Results |
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The endogastric capsule did not cause any side effects and all of the 62 patients were fully compliant with the procedure. The results of tumor marker determinations are shown in Tables 1 and 2. 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. In patients with superficial gastritis or chronic active gastritis, the mean value of CEA was 49.2 ± 25 ng/ml and the mean value of CA 19-9 was 46 ± 48 ng/ml. Patients bearing intestinal metaplasia and dysplasia showed CEA and CA 19-9 values above 100 ng/ml. In the nine cases with intestinal metaplasia, the mean CEA and CA 19-9 values were 165 ± 65 ng/ml and 160 ± 48 ng/ml, respectively. In the six patients with dysplasia, the mean CEA and CA 19-9 values were 225 ± 55 ng/ml and 220 ± 48 ng/ml, respectively. In patients with gastric carcinoma, the mean CEA level was 513.8 ±627 ng/ml and the mean CA 19-9 level was 545 ± 510 ng/ml.
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In a dichotomized analysis of the study population (Table 3), patients with precancerous lesions and cancer showed higher levels of CEA and CA 19-9 than patients with gastritis and controls. This difference was significantly greater than that expected by chance, with a P value <0.001.
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In five cases with positive histology for HP infection, the analysis of gastric juice showed four infections confirmed by both bacteriological and PCR techniques and one was found positive only by PCR. The analysis of gastric juice was negative in the remaining five samples, which showed negative histology for HP infection.
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Discussion |
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Tumor marker levels in gastric juice may have a role in gastric cancer screening, but low-cost and non-invasive procedures in place of upper endoscopy are needed. In this respect, the results of the endogastric capsule seem promising and reliable. The results of CEA and CA 19-9 analyses in gastric juice were not related to age; in the study population, the median age was 55 years and no major imbalance was observed between groups. Also, seven out of the 23 patients with cancer lesions were <50 years old and all of them showed high levels of both tumor markers. Multiple biopsies of gastric mucosa may cause transient elevation of tumor markers in gastric juice even in the absence of high-risk lesions or cancer. In the present study this effect is unlikely, since the endogastric capsule was tested 1 week after upper endoscopy and healthy controls showed low levels of CEA and CA 19-9 in gastric juice. Finally, the ability to detect high levels of both tumor markers did not seem to be related to the tumor stage, the grade of differentiation or the histological subtype.
Tatsuta et al. [14] found that CEA levels tended to be higher in patients with large tumors, or with mucinous production or without glandular structures. However, they did not find any significant difference in CEA measurements between early and advanced cases and between histological subtypes of gastric carcinomas. In two different investigations [8, 9], CEA values were significantly higher in patients with differentiated tumors than in those with poorly differentiated tumors. However, other studies did not find any correlation between common histological features and tumor marker levels in gastric juice. Saito et al. [4] found high CEA levels even in the presence of small lesions and positivity was unrelated to the tumor size. Satake et al. [13] and Bunn et al. [15] found that the extent of disease, the histological classification and the macroscopic appearance of the tumor had no influence on gastric CEA results.
In the present study, CA 19-9 values were significantly higher in patients with cancer than in patients with precancerous lesions, but CEA values did not differ significantly between these two categories. Intestinal metaplasia produces CEA and its concentration in gastric juice may reach comparable values to those reported in the presence of cancer [5, 10, 18, 21]. It is possible that the analysis of tumor markers in gastric juice may not always be effective in differentiating between precancerous lesions and cancer. However, the diagnosis of cancer in its earlier stages and the identification of premalignant conditions in high-risk patients are both relevant to secondary prevention programs and screening.
In addition to radioimmunology assays for determining tumor markers, the endogastric capsule may be used for other analyses of gastric juice. According to our preliminary data, it seems effective in identifying HP infection, which is involved in the overall process of gastric carcinogenesis [3234]. Enhanced production of IL-1ß has been found to be associated with an increased risk of both hypochlorhydria induced by HP infection and gastric cancer [35]; determination of endogastric levels of this important pro-inflammatory cytokine should be investigated. Finally, the endogastric capsule could be used to determine the levels of specific substances such as pepsinogens [23], which are the new and promising targets of ongoing screening studies.
In conclusion, the endogastric capsule provides a novel, effective non-invasive tool for measuring CEA and CA 19-9 in gastric juice. The levels of both tumor markers were found to correlate with histologic findings and in particular, they were useful in identifying patients with high-risk precancerous lesions or gastric carcinoma. This method deserves further investigation, since it may represent an effective strategy for future screening programs.
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Footnotes |
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