Potential of NLS-Investigation In The Pre-surgical Evaluation Of Intramural

Invasion Of Gastric Cancer

K.P. Vasov, S.D. Setkin,

S.A. Skvortsova, G.F. Maretskaya

Gastric cancer in Russia as well as in some other countries all over the world remains one of

the most acute medical problems. Most researchers engaged in the diagnosis and

treatment of gastric cancer have concluded that a timely and early diagnosis can promote

cancer treatments and improve prognostication for the patients.

For many decades radiology and endoscopy remained the principal methods for

diagnosing gastric cancer. The main shortcoming of these methods of investigation is

their inability to obtain a picture of the thick layers of the stomach wall and hence a more

exact data about the extent of tumor invasion into the stomach wall, i.e., the phase of the

tumor process in the pre-surgical period. The first attempts to establish phase gradation

in stomach tumor were made when such investigation methods as computer tomography

(CT), trans-abdominal ultrasound scanning (US) and the most recent NLS investigation

were put into clinical practice. In today’s medicine the NLS investigation may become

an essential method for diagnosing abdominal cavity disease because of its extreme

simplicity, accessibility and non-invasiveness. However, in view of the fact that this

investigation method has been used in medical practice since the late 90, the amount of

the published literature dealing with potentials of the NLS in diagnosing parenchymal

organs is still insufficient.

Rather explicit methods of NLS stomach investigation have been already developed and

some NLS signs of cancer, benign and malignant gastric ulcers have been described (V.I.

Nesterova et.al., 2002). An attempt was made to establish phase gradation of gastric

cancer by means of NLS investigation which resulted in a fairly high accuracy (75.8%) of the

diagnosis mostly due to diagnosing much earlier phases of the tumor process.

According to some authors, NLS offers some incontestable opportunities in defining

phases of gastric tumor mostly located in distal regions of stomach.

Yet, according to most researchers, until recently the NLS had been largely used as a

method for specifying the extent of cancer proliferation, for defining metastases and

malignant invasions beyond the stomach, in other words, the NLS investigation method

enables the diagnosis of stomach tumors even in early phases of the disease.

Most literature dealing with the use of radiological computer tomography to diagnose

stomach tumors provides a proof that this method can potentially be used to diagnose

gastric cancer, especially its endophytic forms. However, most authors still believe that

the principal role of this method lies in acquisition of certain very important information

about the extent of stomach lesion and spread of the process to some adjacent organs.

According to different researchers, the early gastric cancer, that only affects the mucosa and

submucous layer can not be detected on the computer tomograms. In the authors’ opinion,

this is beyond ‘the resolution capabilities’ of this investigation method.

39This work attempted to evaluate the potentials of the noninvasive radiation methods of

investigation (trans-abdominal ultrasound scanning and radiological computer

tomography) in detecting intramural invasion of gastric cancer, and to draw their

comparison characteristics.

The analysis included 72 cases of gastric cancer. All the cases were compared with the

surgical intervention data and the morphological studies of post surgical evidence.

According to the latest gastroenterological TNM classification of tumors (1997), the

group of gastric cancer carriers in phase T1 was 9 (12.5%) cases, T2 8 (11.1%) cases, T3 22

(30.6%) cases and T4 33 (45.8%) cases. Computer linear diagnosis (NLS) and

radiological computer tomography (CT) of the stomach were performed as

supplementary investigation methods deliberately after a preliminary integrated radio-

endoscopic investigation.

Computer tomography of the stomach was done after expanding the stomach walls with a

gas (pneumo-scanning) in standard projections (lying on the back and belly); the trans-

abdominal NLS-investigation of the stomach was performed using the standard

procedure.

In order to more clearly comprehend the NLS and CT signs underlying the pre-surgical

diagnosis of the T-phase of gastric cancer (i.e. invasion degree) one needs to have a clear idea

of the image of a ‘normal’ cancer stomach wall visualized by means of the

investigation method.

Thus, in CT investigation the stomach walls (adequately expanded) were at most 0.3 cm

thick in normal conditions (test group of 50 persons) in all regions with few exceptions in

cardiac and prepyloric regions where the walls were 0.4 cm thick, whereas at an

intramural tumor effect the stomach wall authentically thickened over 0.6 cm (p >0.01).

In most cases it proved to be impossible to differentiate the lamellar structure of the

stomach wall by computer tomography. Changing the section thickness, pitch of the

table and the patients’ posture in the course of scanning facilitated visualization of all the

regions of the stomach very well. The location of the tumor infiltrate to the stomach wall

layers was assumed as a principal criterion whose analysis provided a guide to the extent

of the intramural invasion of the gastric cancer during NLS-investigation, while in

computer tomography the main point was to define the thickness and elasticity of the

stomach wall at the lesion spot.

The point is that NLS-investigation allowed to differentiate tumor quite clearly with

respect to the layers of the stomach wall, while in computer tomography the most

diagnostically important factor was the degree of the stomach wall thickening at the

lesion spot with respect to the neighboring unaffected areas (thickening ratio) along with

some other signs (rigidity, roughness, unevenness). Based on the analysis of the results

of the surgical intervention and morphological investigation of post surgical material as

well as their comparison with NLS and CT data the following conclusions were reached:

both methods are quite potent in pre-surgical determination of the extent of intramural

40invasion of gastric cancer, however the NLS investigation demonstrates a higher

specificity as compared to computer tomography in detecting early phases of gastric

cancer due to visualization of lesion zones in the stomach wall.

Analysis of the investigations enabled discrimination in the NLS-signs that allowed to

define the extent of intramural invasion of gastric cancer.

1. T1 phase: presence of tumor infiltrate within the first layer of the stomach wall,

which is accompanied by hyper-chromogenic density of the wall at the lesion spot (5,

less often 6 points on Flandler’s color scale).

2. T2 phase: tumorinfiltrate within the first and second layers of the stomach wall

accompanied by hyper-chromogenic density of the first two layers (5-6 points at the

lesion spot).

3. T3 phase: a frank chromogeneity of the inner layers of the stomach wall (6 points)

except for the serous layer, which is evaluated at 4 or more often 5 points.

4. T4 phase: lesion of all layers of the stomach wall accompanied by chromogeneity of

the serous membrane (6 points) and signs of tumor invasions into the neighboring

anatomical structures accompanied by a frank chromogeneity (4-5 points) of the

adjacent organs.

Detection of some affected peregastric (regional) lymph nodes and distant metastases in the

course of investigation enabled analyzis of the N and M criterion as well.

With respect to the potentials of computer tomography in pre-surgical determination of

the extent of intramural invasion of gastric cancer, it should be admitted that it had a less

specific pattern and was essentially based on the extent of the stomach wall thickening at the

lesion spot.

Thus, since the CT signs are indicative of one or another degree of gastric cancer

invasion, they could be conditionally classified in the following manner:

- It proved practically impossible to distinguish between tumors in T1 and T2 phases.

So diagnosis was based on the analyses of non-multiple stomach wall thickenings

from 0.3 to 05 cm, with the external outlines being clear and smooth.

- The T-3 phase typically had integer multiple thickenings of the stomach wall over 0.5

cm not accompanied by deformed external outlines of the stomach wall and with no

signs of the tumor spreading beyond the stomach wall.

- The T-4 phase had multiple thickenings of the stomach wall (two, three or more times

as thick) over 0.1 cm with a disturbed integrity of the external outlines of the stomach

wall at the lesion spot and with some signs of tumor invasion into the adjacent

anatomical structures.

According to our information, the NLS-investigation proved to be the most accurate and

specific method of investigation in pre-surgical diagnosis of gastric cancer in its early

phases (T-1, T-2) while CT results appeared to be more convincing in detecting later

phases of tumor lesion (T-3, T-4). It should be noted, that, in our opinion NLS is the most

41accurate method of investigation in detecting remote metastases (p >0.05). Based on the

statistical analyses, the specificity of the NLS method of the investigation in detecting the

T-phase of gastric cancer (with calculations made with reference to T-1, T-1 phases)

amounted to 76%, sensitivity to 74.3% and accuracy to 78.2%, w.r.t. the computer

topography the specificity, sensitivity and accuracy were 70% each (in this case

calculations were made w.r.t. T4-phase of gastric cancer, because differentiating the

lamellar structure of the stomach wall was found impossible in CT investigation).

Thus, as compared to computer tomography, the NLS investigation proved to be a more

specific method for diagnosing cancer in its early phases although in a number of cases it was

found difficult to differentiate between T1-T3 phases of a tumor lesion. In CT

investigation T1-T2 phases were defined conventionally based on the degree of stomach wall

thickening the lesion spot. NLS did not succeed in imaging anatomical structures beyond the

stomach wall as distinctly as CT investigation did, but NLS was more

efficient in evaluating such characteristics as M and N.

So, an integrated approach to the use of NLS investigation and radiological computer

tomography has proved to be more preferable for more accurate pre-surgical diagnosis of

intramural invasion of gastric cancer, however the order of priority and efficiency in their use

somewhat depend on the results of primary radio-endoscopic investigation of the

stomach. In addition it should be noted, that contra-distinction of these methods of

investigation in diagnosing and phasing of gastric cancer against each other would be a

mistake and delusion.

In conclusion, it should be emphasized that despite their subordinate use with reference to

radiological and endoscopic methods of gastric cancer investigation, the NLS

investigation and radiological computer tomography should be brought into line with

primary methods of stomach investigation.

The conclusion is based on the facts that unlike some conventional radiological and

endoscopic methods of investigation they allow to evaluate the internal structure of the

stomach wall, which is a major factor in the pre-surgical detection of intramural invasion.

This enables to work out the proper approach for treating patients affected by gastric

cancer, and based on the well-founded data reject the explorative laparatomy in case of an

obvious process. Considering general accessibility, lack of radiation exposure and

application simplicity it appears more appropriate to use NLS investigation as the most

preferable of the above mentioned methods.

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