Gastric carcinoma is the fourth most common cancer and the second leading incidence of cancer worldwide. Locally advanced cancer is that cancer which has spread from its point of origin to nearby tissue or lymph nodes. Treatment of gastric cancer remains an urgent problem. In recent years, some advances have been made in the field of adjuvant therapy for patients with locally advanced gastric cancer 1.

Gastric cancer is one of the most common malignant neoplasms and is the fifth leading cause of cancer mortality in western populations, despite its decreasing incidence in Europe and the United States 2. In the majority of patients, gastric cancer is usually diagnosed at a later stage of the disease progression when there are classic symptoms of weight loss, persistent dull pain in the epigastrium and loss of appetite. In 8% of cases he is detected in the form of early gastric cancer (EGC) during the mildly symptomatic or asymptomatic phases 3.

The severity of gastric cancer is associated with the depth of invasion (lesion depth) along the layers of the stomach wall, infiltration to regional lymph nodes and the presence of metastases to adjacent and distant organs (TNM classification). Depending on the degree of damage of the layers of the wall of the stomach the pathology can be classified into Early and Advanced gastric cancer (EGC and AGC) 4. Diagnosis of early gastric cancer in Western countries is 5-15%, when in Japan it reaches 30-50%. According to the results of 20 years of research Ahn XC (2011), EGC to progress to an advanced stage of takes about 8 months 5.

Literature definitions of Locally-advanced gastric cancer are controversial. Some researchers believe that AGC starts from T2, and others - from T3 678. According to Han S-K. (2012) ‘Locally advanced gastric cancer’ is a tumor of T4b (adjacent organ invasion) or inoperable tumour due to adjacent organ invasion or bulky LNs without distant metastasis. Another defines, ‘Locally advanced gastric cancer’ as a tumor, which may be a ‘resectable’ cancer when compared with M1 advanced ’cancer 9.

To determine the extent of Advanced gastric cancer Sol A.D. et al. (2014) analyzed the literature on this controversy. The results of the studies gave rise to the following conclusion 10: It is difficult to differentiate between resectable advanced stage, unresectable M0 and M1 cancers using the term ‘advanced’. It must be noted that ‘advanced gastric cancer’ may imply a number of stages of the disease and studies must highlight the exact clinical TNM classification for evaluation of the study.Accurate preoperative staging is therefore essential for optimal surgical management with consideration of preoperative and/or postoperative chemotherapy 11. The most commonly used technique for the staging of GC is multidetector computed tomography (MDCT) as it provides higher resolution images 12. The high efficiency of endoscopic ultrasonography (EUS) in assessing the depth of invasion is considered only in early gastric cancer (EGC) 1314.

Currently, the application of transabdominal ultrasonography in the diagnosis of gastric diseases is insignificant. However, in previously published articles, the capability of the method in differentiating the layers of the stomach wall, and to diagnose pyloric stenosis in cancer of the output section of the stomach is clearly demonstrated 15.

Objective

The aim of this study was to evaluate the capabilities of transabdominal ultrasonography in the assessment of structures and functional disorders of locally advanced gastric cancer of various locations.

The study design included 61 patients with locally advanced gastric cancer. 36 (59,0%) cases were males (mean age 62.7 years) and 25 (41,0%) females (mean age 59.3 years). All patients were on surgical treatment at the Kharkov Regional Oncology Center (Ukraine).

Histology results showed, in 58 (95,1%) cases adenocarcinoma, and in 3 (4,9%) – ring-cell carcinoma (cricoidal) gastric cancer was established. According to the classification by the American Joint Committee on Cancer (AJCC) 16, the stage of T2 was confirmed – in 16 (26,2%) cases, the stage of T3 – in 41 (67,2%) cases and the stage of T4 – in 4 (6,6%) cases . The diverse locations of gastric tumor was established as follows; in 29 (47.5%) cases antrum, in 27 (44,3%) cases – the body, in 5 (8.2%) cases- the cardia and fundus (Table 1).

All the patients underwent preoperative X-ray, virtual gastroscopy techniques, multidetector computed tomography (MDCT) and transabdominal ultrasonography (TAS).

Normal ultrasound features was shown in 35 patients without gastric pathology. TAS was carried out with the convex and microconvex transducers in the frequency range of 2-5 MHz and 4-7 MHz respectively in B and color Doppler modes.

TAS of an empty stomach visualizes only the abdominal part of the esophagus which is 3-4 cm long. In the center of the esophagus, the mucosa of both walls is well defined as a thin hyperechoic linear structure. The walls of the unchanged esophagus have a linear layered structure (Figure 1).

Immediately after contrasting, bubbles of gas appear in the cavity of the stomach, which gradually disappears. The thickness of the stomach wall in the region of the subcardiac part and the bottom is not more than 4 mm, the layers of the wall are not well differentiated, and there are no local thickenings (Figure 2).

In the area of the body all the gastric wall layers are clearly differentiated. The gastric wall thickness when filled with the fluid does not exceed 3 mm (Figure 3). During peristaltic waves, there is also thickening of the gastric wall, which disappears after a few seconds. The greatest wall thickness of 3-5mm is observed in the antrum part. A careful monitoring illustrates the opening and closing of the pyloric canal (Figure 4).

To diagnose a locally advanced gastric cancer, the following echographic symptoms were elicited:

1. Local thickening of the gastric wall more than 6 mm.

2. Deterioration or absence of differentiation of the layers of the gastric wall.

3. Decreased or absence of local peristaltic waves.

4. Presence of parietal formations protruding into the gastric cavity and outside peristaltic waves.

5. The maximum thickness and extent of the affected area of the stomach.

6. The maximum diameter of the pyloric canal during the passage of the peristaltic wave

The polypoid type of gastric cancer was observed in 3 (4,9±2,8%) cases, the ulcerative type – in 18 (29,5±5,8%), the infiltrative ulcerative type – in 27 (44,3±6,4%) and the diffuse infiltrative type – in 13 (21,3%±5,2%) cases respectively (Table 2). On the echogram, the tumor was

Visualized as a polypoid formation on a wide base above the gastric mucosa of a non-uniform structure, an irregular surface (Figure 5, Figure 6, Figure 7).

T2 stage of diffuse carcinoma was recorded in 14 cases – among them 5 cases of ulcerating forms, 5 cases of infiltrative ulcerative forms and 4 cases of diffuse infiltrative forms. Gastroscopy diagnosis was established in all 10 cases of ulcerative and infiltrative ulcerative forms of gastric carcinomas and in 3 cases of diffuse infiltrative forms. Ultrasound diagnosis was established in 13 cases of diffuse carcinoma, except for one case where the location of the ulcerative form was in the fundus of the stomach (Figure 8, Figure 9, Figure 10).

T3 stage of polypoid form was recorded in one case, ulcerative form – in 11 cases, infiltrative ulcerative forms – in 21 cases and diffused infiltrative forms – in 8 cases. The Sonographic features of infiltrative ulcerative form of gastric carcinoma was shown as local uneven thickening of the stomach wall with a length of up to several centimeters with intermittent images and ulceration of the mucosa (Figure 11). The Ulcerative form of gastric carcinoma was shown as a raised margins surrounded by a thickened gastric wall with irregular margins (Figure 12). Gastric carcinomas of diffuse infiltrative form is illustrated as a diffuse thickening of the muscle layer, a smooth contour, discontinuous mucosal image without ulceration and involvement of the serous membrane in the process (Figure 13).

Distal gastric cancer was observed in 24 (39,3%) cases and contributed to the development of pyloric stenosis: in 6 (9,8%) cases it was compensated, in 18 (29,5%) – was sub compensated. The layers of the wall were not differentiated in all patients with sub compensated pyloric stenosis. In the case of compensated pyloric stenosis, the thickness of the affected area was 10,2±2,9mm, the length was 27,1±6,2mm, the diameter of the pylorus was 8,3±0,8mm (Figure 14). Among patients with sub compensated pyloric stenosis, the thickness of the stomach wall was 19,8±4,1mm, the length was 43,6±4,5mm, the pyloric diameter was 4,3±1,1mm (Figure 15).

Moschetta M. et al. (2011) suggested a new method for CT reconstruction which improves the diagnostic accuracy of the GC T-set 17. Vessel probe, initially developed for examination of small vessels can display images in orthogonal multiplanar, oblique and curved reconstructions as well as three-dimensional and curved reformat views. The vessel probe algorithm permits a more accurate view of gastric wall stratification due to the reduction of the partial volume artifact.

Color Doppler mode was used to assess the nature of the gastric wall lesion in pathologically thickened areas. This method allows the recording of blood flow in the altered areas and using the degree of vascularization to differentiate gastric cancer and other benign changes. Usually in a normal gastric wall it is not possible to visualize the vessels.

Among the 61 patients, pathological vascularization was detected in 42 (68.8%) cases. Of these, all 4 (6.5%) patients with gastric cancer were stage T4 and 38 (62.3%) were stage T3. In 13 cases, vascularization was weak, in 24 cases - moderate, and in 5 cases - enhanced.

Among the 61 patients, pathological vascularization was detected in 42 (68.8%) cases. Of these, all 4 (6.5%) patients with gastric cancer were stage T4 and 38 (62.3%) were stage T3. In 13 cases, vascularization was weak, in 24 cases - moderate, and in 5 cases - enhanced.

Weak vascularization was manifested in the form of a single point color vascular signals, the moderate vascularization - in the form of linear color vascular signals and the enhanced vascularization - in the form of wide color areas inside the tumor (Figure 16, Figure 17).

Metastasis to the regional lymph nodes was diagnosed in 52 cases. Ultrasonographically, this was detected in 37 (71.2%) cases. Sonographic features of lymph node metastatic lesions are: an increase in their thickness, a decrease in echogenicity, deterioration or lack of differentiation of the peripheral and central parts of the nodes, recording of color vascular signals inside the nodes (Figure 18, Figure 19).

It is an established fact that, upper gastrointestinal endoscopy and endoscopic ultrasonography are the main methods for diagnosing early gastric cancer 1418. Because there are no clinical symptoms for early gastric cancer, these methods can better be utilized in screening programs which is not done in most countries. As a consequence of the gastric cancer screening program in Japan, there is a high rate of early detection 4.

Endophytic growth of gastric cancer for a very long time can remain outside the diagnostic capability of endoscopic and X-ray examination. In such cases, multi-detector computer tomography is the most widely used and effective method 19. In the differentiation of the layers of the stomach wall, especially of its output and body sections, ultrasonography demonstrates a good capability 15.

A computer tomography reconstruction method alternatively, allows for the visualization of vessels in the affected part of the stomach 17.  As shown in our study, ultrasonography in tissue mode and color Doppler allows for the visualization of vessels in pathologically thickened areas of the stomach, this can therefore be used to adjudge the intensity and the degree of malignancy of the process.

Diagnosis of lymph nodes involvement in the pathological process allows us to determine the prevalence of gastric cancer and predict survival rate after surgical resection. Double contrast-enhanced ultrasonography is a non-invasive, convenient and reproducible method for the evaluation of LN metastasis in EGC and pre-operative prognosis of EGC 20.

The overall accuracy, sensitivity and specificity of N staging with MDCT are 79% (69–92%), 84.6% (78–92%) and 73.9% (62–85.7%) respectively 2122. There is increasing evidence that examination of an insufficient number of lymph nodes may have a detrimental effect on the overall survival rate of patients with GC who receive treatment 23.

In our study, the frequency of visualization of pathologically affected lymph nodes reaches 71%.

In the diagnosis of locally advanced gastric cancer, ultrasonography demonstrates a very good capability for determining the extent and depth of the affected area. In the color Doppler mode, the method allows to study the vascularization of a locally thickened area, as well as adjacent enlarged lymph nodes, which is very important in the determination of the degree of malignancy of the hyperplastic process. Ultrasonography can independently determine the degree of pyloric stenosis in patients with distal gastric cancer.