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for gastric cancer, the proportion of disease revealed in its initial forms increases to 30-40%, while mass-scale screening of a whole population increases this to 45.7% [143, 223]. This implies that further advances in gastric cancer control depend largely on improvement of the organizational system, based on the principle of active detection of the disease at the stage when, in the absence of clinical symptoms, the patient does not seek medical aid (D Fig. 151).

The problem of screening for gastric cancer has long been discussed in the medical literature. The authors allude to the experience of Japan, which developed and introduced to practical use a program for active detection of gastric cancer. The program is oriented at diagnosis of the early forms of gastric cancer and is based on radiological examination with subsequent selective endoscopy. Thus, the 5-year survival is on the whole higher among patients in whom gastric cancer was diagnosed as a result of screening than among patients in whom the disease was diagnosed during a visit to the doctor (86% versus 61%, respectively) [134].

In Russia, the program of selective screening for gastric cancer, based on an initial X-ray examination with subsequent selective endoscopy, was undertaken in the Moscow region (population 5 mil lion) [57, 58, 223]. MONIKI is one of the medical institutions where, in 1980, a special department was equipped with a Toshiba unit for gastrofluorogra-phy of the stomach. We have examined more than 36 000 patients. This made it possible to summarize the accumulated experience in selective screening for gastric cancer [52, 56, 57].

An important stage was the formation of groups of persons who were examined by X-ray methods. Most of the subjects selected were patients who did not have any special complaints of gastric dysfunction but were assigned to the risk group for gastric cancer. They were selected by questioning at various clinical departments (hematological, endocrinological, neurological, and others). The following factors were taken into account: familial susceptibility, longstanding nutritional disorders, abuse of alcohol or smoking tobacco, and other risk factors. In addition, we conducted planned outpatient examinations of subjects with chronic diseases of the stomach, mostly chronic gastritis with reduced acidity of the gastric juice, anemic patients, and patients who visited the doctor for the first time because of various forms of gastric discomfort.

Using standard methods, we effectively examined a very large number of patients. In the absence of organic pathologies, X-ray views were taken in the standard projections and subsequently studied (the obligatory component of examination). If changes were detected in the stomach, the number of X-ray views necessary was decided by the radiological diagnostician individually in each particular case.

In evaluating the results, we want to point out the advantages of test examinations, during which the proportion of detected tumors of the stomach extending over a distance 3-4 cm was three times less than during examination of patients with clinical signs of gastric pathology. On the whole, of the 36 000 selectively screened subjects, gastric cancer was diagnosed in 680 patients (1.94%); in 170 of them (25%) the muscular coat was not invaded (D Fig. 152) [75].

□ Fig. 152a-d. Patient Z., age 58. Diagnosis: gastric cancer. a Stomach roentgenogram (tight filling, vertical position, anterior projection): uneven contour of the lesser curvature (arrow). b Stomach roentgenogram (tight filling, vertical position, left half-oblique projection), dosed compression: more distinctly visualized is uneven contour of the lesser curvature of the antral part (arrow). c, d Stomach roentgenograms (double contrast, horizontal position, right anterior oblique projection): the wall of the lesser curvature is thickened and rigid due to intramural infiltration (arrow). Conclusion: Infiltrative cancer of the lesser curvature of the antral part of the stomach.

□ Fig. 152a-d. Patient Z., age 58. Diagnosis: gastric cancer. a Stomach roentgenogram (tight filling, vertical position, anterior projection): uneven contour of the lesser curvature (arrow). b Stomach roentgenogram (tight filling, vertical position, left half-oblique projection), dosed compression: more distinctly visualized is uneven contour of the lesser curvature of the antral part (arrow). c, d Stomach roentgenograms (double contrast, horizontal position, right anterior oblique projection): the wall of the lesser curvature is thickened and rigid due to intramural infiltration (arrow). Conclusion: Infiltrative cancer of the lesser curvature of the antral part of the stomach.

A comparison of the efficacy of gastric cancer detection by various screening programs shows that screening of risk groups is more effective. As we have already indicated, the frequency of gastric cancer detection in such investigations is 1.94%, much higher than the average in mass-scale screening in Japan (0.12%) or in the countries of Latin America (0.4%). However, in selective screening, only subjects predisposed to tumor disease are examined, and the percentage of cancer patients detected is therefore much higher than during mass-scale outpatient screening. While estimating the frequency of early gastric cancer detection, it is necessary to indicate that selective screening programs are much less effective compared with mass-scale screening of a population. In Japan, for example, early gastric cancer was diagnosed in 57.6% cases of cancer patients, whereas at MONIKI the rate was only 25%. The main objective of any screening program is to reduce mortality and to increase the 5-year survival. Although these parameters are far worse at MONIKI than in Japan, we can still report a sufficiently high efficacy of selective screening, because the 25% frequency of early gastric cancer detection is much higher than the statistical average at specialized hospitals in Russia and in most other countries (5-7%).

X-ray examinations of the stomach according to the complex standard method worked out at MON-IKI to evaluate the efficacy of selective screening for gastric cancer included fibergastroscopy with biopsy as the main additional method of examination. Endoscopy was indicated for subjects with any deviation from the X-ray standard, namely, malignant and benign tumors, ulcers, marked hypertrophy of the mucosal folds, including Menetrier's disease, various deformations of the stomach, etc. Patients who needed a additional examination were directed to the endoscopist. These amounted to 6-7% of the X-ray examined subjects, not exceeding 3-4% in the group of outpatient subjects who had no significant complaints, and 8-9% of patients with marked gastric complaints (D Fig. 153) [30, 56, 223].

Since gastrofluoroscopy does not rule out the danger of ionizing radiation for large population groups, equivalent and effective doses were first measured. Tissue doses were determined by the method of thermoluminescent dosimetry on an anthropomorphic phantom, with full modeling of con ditions of the method worked out. The overall time of 60 exposures was determined; simultaneously, we determined the duration of exposure to high voltage at all stages of the cycle. The total time of radiation exposure was 33 s. It appeared that during fluoros-copy of the stomach, the equivalent load on the bone marrow, the stomach, the liver, the kidneys, and the spleen is much lower according to our program than with other modifications ofX-ray examinations. The effective dose was about 1.43 mSv. Note that the effective dose in traditional fluoroscopy with image enhancement (without spot filming) is 2.2 mSv, and without image enhancement - 4.2 mSv/min; with one X-ray picture taken, the equivalent dose is 1.1 mSv. Thus, screening according to our method significantly reduces the effective dose. Modern digital X-ray units reduce it by 20-30 times, some of them even by 40 times. By using computer technologies to process the findings and doing away with

▲ Fig. 153 b.

□ Fig. 153a-c. Patient L., age 61. Diagnosis: gastric cancer. Complaints of gastric discomfort after meals. Occasional vomiting in the evenings. a Stomach roentgenogram (tight filling, vertical position, anterior projection): the sinus and the antral part are ectatic; marked deformation of the pyloric part. b Stomach roentgenogram (tight filling, vertical position, anterior projection): the pyloric part is unevenly narrowed due to circular infiltration; the evacuation function of the pylorus is disordered. c Stomach roentgenogram (double contrast, horizontal position, anterior projection): the walls of the pyloric part are thickened and rigid, the intramural infiltration spreads to the lesser curvature of the antral part of the stomach (arrows). Conclusion: Infiltrative cancer of the pyloric part of the stomach. Endoscopy reveals marked narrowing of the pyloric part of the stomach. Histological examination of the bioptates taken during endoscopy verified signet-ring cell carcinoma.

film technology, the radiologist will be able to increase the zone of his interest, increase or decrease the contrast of the image, measure the extent of infiltration of the stomach wall, conduct three-dimensional reconstruction, etc. The effective dose in these cases will be so insignificant that the discussion about the danger of ionizing radiation for the patient will be precluded.

China conducted its own screening. Their method was based on determining micro amounts of blood in gastric contents. A patient swallows a test strip, which is then pulled back from the stomach with a thin string within a few minutes. If blood is contained in the stomach in micro quantities, the strip changes color. In other words, this is a qualitative test for the presence of blood in the stomach. The test should by no means be considered specific for

▲ Fig. 153 c.

gastric cancer. Moreover, it cannot detect early cancer: The tumor must be ulcerated in order to release blood into the stomach cavity. It therefore follows that this test cannot be used in screening for gastric cancer. Its only indisputable benefit is low cost.

An active search for ways to increase the efficacy of the method with simultaneous reduction of its cost continues. Screening for pre-cancerous conditions is one of them. It has long been known that patients with atrophic gastritis are a risk group for gastric cancer. It has been established that decreased concentration of pepsinogen I and a changed pep-sinogen I-to-pepsinogen II ratio closely correlates with atrophy of the gastric mucosa. ELISA data on serum pepsinogen I also indicate its reduced concentration in gastric cancer patients: the lower the differentiation, the lower this level. But the pepsinogen I level is lower in patients with chronic atrophic gastritis than in patients with highly differentiated cancer of the stomach.

In healthy subjects, the pepsinogen I level in the serum is 123.6 ±11.7 ng/ml. In patients with highly differentiated gastric cancer it is 58.2 ±3.5 ng/ml, in those with less differentiated cancer 37.4 ±3.4 ng/ml, and in patients with atrophic gastritis 51.1 ±4.7 ng/ ml [25].

It is believed that the sensitivity and specificity of determination of the pepsinogen level for the diagnosis of gastric cancer in the screening program are 84.6% and 73.5%, respectively. This is not bad for an indirect diagnostic method. But it should be remembered that this approach may be informative for the detection of only certain types of gastric cancer, i.e., cancers originating in the presence of atrophic gastritis, namely, distal gastric cancer. Atrophic changes are not an obligatory companion of proximal cancer of the stomach, the incidence of which has increased dramatically in recent years. A similar situation occurs with inclusion of serological markers of antibodies to H. pylori in screening pro grams, because it is mostly distal cancer of the stomach that is associated with H. pylori infection. It follows that if we use these screening programs, we will miss one third of gastric cancer patients. Such screening by no means meets our requirements. In addition, many problems require verification as regards H. pylori. The problem needs thorough studies.

It can thus be definitely concluded that, in the near future, screening programs based on the traditional X-ray examination with subsequent selective endoscopy will remain one of the most effective ways of increasing the efficacy of gastric cancer detection, especially at its early stages. It should be admitted, however, that mass-scale screening of a population for gastric cancer is an expensive enterprise and can be conducted only with adequate financial support from the government. As for Russia, selective screening may be acknowledged as practicable based on financial considerations, although its efficiency in revealing early forms of gastric cancer is lower. Therefore, it is necessary to be especially careful in selecting subjects into risk groups, and this work should be done by physicians of prophylactic and therapeutic medical institutions.

Of course we do not mean the extensive use of gastrofluorography, which is now outdated. But experience in selective screening, which has been accumulated at MONIKI, suggests its sufficiently high efficiency. In accordance with the concept adopted by the Ministry of Health of the Russian Federation concerning the development of radiological diagnosis up to 2010, this method can become the basis for early diagnosis of gastric cancer.

To conclude the discussion of screening for gastric cancer, it is necessary to emphasize some aspects which, we think, include all major problems connected not only with screening but with the general gastric cancer problem. Unfortunately, some are of the opinion that the study of most problems connected with gastric cancer has already been completed. They refer to the diagnosis of gastric cancer, where the leading role belongs to endoscopy. They also refer to treatment, where the main efforts are directed at further introduction of surgical operations into practical medicine; this can help patients with pronounced forms of cancer. But they almost completely disregard the problem of diagnosing gas tric cancer in its initial stages. This discouraging situation will not change as long as this tendency persists, and this is especially discouraging, because gastric cancer makes up 10-12% of all oncological diseases in most regions of the world, Russia included.

In our monograph we have tried to demonstrate the infeasibility of excluding radiological diagnosis, first and foremost the traditional X-ray examination, from the algorithm for diagnosing gastric cancer. We have produced convincing evidence and explanations for the indispensability of the X-ray, which should be used along with en-doscopy.

The current morphological and clinical characteristics of gastric cancer suggest that only the combined use of X-ray and endoscopy can change the discouraging situation with regard to relatively early diagnosis of the disease. Radical change is also very difficult without screening. Selective screening may become a reasonable alternative in countries with limited economic potential, Russia included. It is very important to attach greater importance to outpatient services in the attempt to improve the control of the disease. Diagnosis and treatment might thus be radically facilitated. Therefore, the tendency to minimize outpatient use of X-ray examinations works against improving the diagnosis of gastric cancer. All these aspects are discussed in detail in the monograph.

Although the main purpose of the monograph is to describe the current role of the X-ray examina tion in the diagnosis of gastric cancer, the book also covers some problems related to the epidemiology and morphology of the disease in order to disprove the existing underestimation of X-ray potential in early diagnosis.

While describing radiological diagnosis, we dwell on its methodological and semeiotic principles, as well as on the special importance of each method. These include the traditional radiological and ultrasonographic methods, computed tomography, and magnetic-resonance imaging. While we value these methods, above all MRI, unlike some other researchers, we rely not only on endoscopy but also on the traditional X-ray, because we believe it greatly increases the objective value of the findings and potentials of each separate method.

A special chapter in the monograph is dedicated to our view of the relationship between endoscopy and X-ray in the diagnosis of gastric cancer. The particular value of the clinical findings, which are included in practically all chapters, is their dependability based on surgical and anatomical evidence.

We realize that it will be very difficult to change existing views on gastric cancer diagnosis, where priority is given to endoscopy alone.

This position is, unfortunately, taken not only by health-care authorities and most clinicians, but also by some leading radiological diagnosticians. All we can do is ask them to read this monograph, which is based on more than 30 years of continuous practical experience. It is our firm conviction that this book can contribute to solving the vitally important problem of diagnosing gastric cancer.

References

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