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الكلية كلية الطب
القسم الجراحة
المرحلة 4
أستاذ المادة كاظم جلوب حسن اللامي
5/9/2011 9:00:44 AM
GASTRIC CANCER
Carcinoma of the stomach is a major cause of cancer mortality worldwide. Its prognosis tends to be poor with cure rates little better than 5–10%, although better results are obtained in Japan where the disease is common. Gastric cancer is actually an eminently curable disease provided that it is detected at an appropriate stage and treated adequately. It rarely disseminates widely before it has involved the lymph nodes and, therefore, there is an opportunity to cure the disease prior to dissemination. Early diagnosis is therefore the key to success. Unfortunately, the late presentation of many cases is the cause of the poor overall survival figures. The only treatment modality able to cure the disease is resectional surgery.
Incidence
There are marked variations in the incidence of gastric cancer worldwide. In Japan the disease is much more common, with an incidence of approximately 70 cases per 100 000 population per year. In general, men are more affected by the disease than women and, as with most solid organ malignancies, the incidence increases with age.
At present, marked changes are being observed in the west in terms of the incidence and sites of gastric cancer and the population affected, changes that to date have not been observed in Japan. First, the incidence of gastric cancer is continuing to fall, at a rate of about 1% per year, with the reduction exclusively affecting carcinomas arising in the body of the stomach and the distal stomach. In contrast, the incidence of carcinoma in the proximal stomach, particularly the oesophagogastric junction, appears to be increasing. Carcinoma of the distal stomach and body of the stomach is most common in low socio-economic groups, whereas the increase in proximal gastric cancer seems to affect principally higher socio-economic groups. Proximal gastric cancer does not seem to be associated with H. pylori infection, in contrast with carcinoma of the body of the stomach and the distal stomach.
Aetiology
Gastric cancer is a multifactorial disease (CorreaH. pylori seems to be principally associated with carcinoma of the body of the stomach and the distal stomach rather than the proximal stomach. As Helicobacter is associated with gastritis, gastric atrophy and intestinal metaplasia, the association with malignancy is perhaps not surprising. Several other risk factors have been identified as being important in the aetiology of gastric cancer. Patients with pernicious anaemia and gastric atrophy are at increased risk, as are those with gastric polyps. Patients who have had peptic ulcer surgery,particularly those who have had drainage procedures such as Billroth II or Pَlya gastrectomy, gastroenterostomy or pyloroplasty, are at approximately four times the average risk.
Presumably, duodenogastric reflux and reflux gastritis are related to the increased risk of malignancy in these patients. Intestinal metaplasia is a risk factor. Carcinoma is associated with cigarette smoking and dust ingestion from a variety of industrial processes. Diet appears to be important, as illustrated by the often quoted example of the change in the incidence of gastric cancer in Japanese families living in the USA. The ingestion of spirits may induce gastritis and, in the long term, cancer. Excessive salt intake, deficiency of antioxidants and exposure to N-nitroso compounds are also implicated. The aetiology of proximal gastric cancer remains an enigma. It is not associated with Helicobacter but is associated with obesity and higher socio-economic status. Genetic factors are also important but imperfectly elucidated .
Clinical features
The features of advanced gastric cancer are usually obvious. However, curable gastric cancer has no specific features to distinguish it symptomatically from benign dyspepsia. The key to improving the outcome of gastric cancer is early diagnosis and, although in Japan there is a screening programme, most curable cases are picked up by the liberal use of gastroscopy in patients with dyspepsia. However,a high index of suspicion is necessary, as endoscoping only patients with symptoms of advanced canceris unlikely to be beneficial because such patients are not surgically curable. It is important to note that gastric anti-secretory agents will improve the symptoms of gastric cancer so the disease should be excluded preferably before therapy is started. In advanced cancer, early satiety, bloating, distension and vomiting may occur. The tumour frequently bleeds, resulting in
iron-deficiency anaemia. Obstruction leads to dysphagia, epigastric fullness or vomiting. With pyloric involvement the presentation may be of gastric outlet obstruction, although the alkalosis is usually less pronounced or absent compared with cases of duodenal ulceration leading to obstruction. Metastatic lymph nodes may be palpable, most notably in the left supraclavicular fossa (Virchow’s node, Troisier’s sign). In recent years, gastric outlet obstruction has been more commonly associated with malignancy than benign disease. Non-metastatic effects of malignancy are seen, particularly thrombophlebitis (Trousseau’s sign) and deep venous thrombosis. These features result from the effects of the mour on thrombotic and haemostatic mechanism.
Site
The proximal stomach is now the most common site for gastric cancer in the west. Because so many malignancies occur at the oesophagogastric junction, and because the lower oesophagus is also a very common site of adenocarcinoma, it is artificial to separate the stomach from the oesophagus. Therefore, it is best to consider the whole of the uppergastrointestinal tract from the cricopharyngeus to the pylorus. The incidence of cancer at these various sites is show that just under 60% of all of the malignancies occurring in the oesophagus and stomach occur in proximity to the oesophagogastric junction.this high prevalence of proximal gastric cancer is not seen in Japan, where distal cancer still predominates, as it does in most o fthe rest of the world.
Pathology
The most useful classification of gastric cancer is the Lauren classification. In this system there are principally two forms of gastric cancer: intestinal gastric cancer and diffuse gastric cancer. Inintestinal gastric cancer, the tumour resembles carcinomas found elsewhere in the tubular gastrointestinal tract and forms polypoid tumours or ulcers. It probably arises in areas of intestinal metaplasia. In contrast, diffuse gastric cancer infiltrates deeply into the
stomach without forming obvious mass lesions but spreading widely in the gastric wall. Not surprisingly, this has a much worse prognosis. A small proportion of gastric cancers are of mixed morphology.
Gastric cancer can be divided into early gastric cancer and advanced gastric cancer. Early gastric cancer can be defined as cancer limited to the mucosa and submucosa with or without lymph node involvement (T1, any N);
In the Japanese classification, early gastric cancer can be protruding, superficial or excavated. Early gastric cancer is eminently curable, and even early gastric cancers associated with lymph node involvement have 5-year survival rates in the region of 90%. In Japan, approximately one-third of gastric cancers diagnosed are in this stage. However, in the UK it
is uncommon to detect gastric cancers at this stage. A number of reasons probably still accounts for this. First, because gastric cancer is less common in the UK, dyspeptic patients are not always referred for endoscopy at an appropriate stage. Second, endoscopists are unfamiliar with the appearances of early gastric cancer and in all probability many such cases are missed. Advanced gastric cancer involves the muscularis. Its macroscopic appearances have been classified by Bormann into four types. Types III and IV are commonly incurable.
Staging
Spread of carcinoma of the stomach
No better example of the various modes by which carcinoma spreads can be given than the case of stomach cancer. It is important to note that this distant spread is unusual before the disease spreads locally, and distant metastases are uncommon in the absence of lymph node metastases. The intestinal and diffuse types of gastric cancer spread differently. The diffuse type spreads via the submucosal and subserosal lymphatic plexus and it penetrates the gastric wall at an early stage.
Direct spread
The tumour penetrates the muscularis, serosa and ultimately adjacent organs such as the pancreas, colon and liver.
Lymphatic spread
This is by both permeation and emboli to the affected tiers of nodes. This may be extensive, with the tumour even
appearing in the supraclavicular nodes (Troisier’s sign). Unlike malignancies such as breast cancer, nodal involvement does not imply systemic dissemination. Blood-borne metastases
Blood-borne metastases occur first to the liver and subsequently to other organs, including lung and bone. They are uncommon in the absence of nodal disease.
Transperitoneal spread
This is a common mode of spread once the tumour has reached the serosa of the stomach and indicates incurability. Tumours can manifest anywhere in the peritoneal cavity and commonly give rise to ascites. Advanced peritoneal disease may be palpated either abdominally or rectally as a tumour ‘shelf’. The ovaries may sometimes be the sole site of transcoelomic spread (Krukenberg’s tumours). Tumour may spread via the abdominal cavity to the umbilicus (Sister Joseph’s nodule). Transperitoneal spread of gastric cancer can be detected most effectively by laparoscopy and cytology.
Lymphatic drainage of the stomach
Understanding the lymphatic drainage of the stomach is the key to comprehending the radical surgery of gastric cancer. The
Table 60.5 International Union Against Cancer (UICC) staging of gastric T1 Tumour invades lamina proporia
T3 Tumour involves serosa
T4 Tumour invades adjacent organs
N0 No lymph nodes
N1 Metastasis in 1–6 regional nodes
N2 Metastasis in 7–15 regional nodes
N3 Metastasis in more than 15 regional nodes
M0 No distant metastasis
M1 Distant metastasis (this includes peritoneum and distant lymphatics of the antrum drain into the right gastric lymph node
superiorly and the right gastroepiploic and subpyloric lymph nodes inferiorly. The lymphatics of the pylorus drain into the right gastric suprapyloric nodes superiorly and the subpyloric lymph nodes situated around the gastroduodenal artery inferiorly.The efferent lymphatics from the suprapyloric lymph nodes converge on the para-aortic nodes around the coeliac axis, whereas the efferent lymphatics from the subpyloric lymph nodes pass up to the main superior mesenteric lymph nodes situated around the origin of the superior mesenteric artery. The lymphatic vessels related to the cardiac orifice of the stomach communicate freely with those of the oesophagus. The prognosis of operable cases of carcinoma of the stomach depends on whether or not there is histological evidence of regional lymph node involvement. Retrograde (downwards) spread may occur if the upper lymphatics are blocked. In Japan, lymph node dissection is highly advanced and the Japanese Research Society for Gastric Cancer has assigned a number to
each lymph node station to aid the pathological staging (Fig. 60.30). Many centres in the west now perform surgery that
involves a radical lymphadenectomy but, in other centres, both the staging and surgery are less developed.
Operability
It is important that patients with incurable disease are not subjected to radical surgery that cannot help them, hence the value of CT/PET (see Fig 60.9, p. 1051). Unequivocal evidence of incurability is haematogenous metastases, involvement of the distant peritoneum, N4 nodal disease and disease beyond the N4 nodes, and fixation to structures that cannot be removed. It is important to note that involvement of another organ per se does not imply incurability, provided that it can be removed. Controversies with respect to operability include N3 nodal involvement and involvement of the adjacent peritoneum; such surgery is performed in Japan but seldom elsewhere. Curative resection should be considered on the remaining patients. Most operable patients should have neoadjuvant chemotherapy as described below, as this improves survival.
Subtotal gastrectomy
For tumours distally placed in the stomach it appears unnecessary to remove the whole stomach. However, a subtotal gastrectomy is very similar to a total gastrectomy except that the proximal stomach is preserved, the blood supply being derived from theshort gastric arteries. Following the resection, the simplest form of reconstruction is to close the stomach from the lesser curve, near the oesophagogastric junction, with either sutures or staples and then perform an anastomosis of the greater curve to the jejunum . Although the reconstruction can be performed as in a Billroth II-/Pَlya-type gastrectomy, this may result in quite marked enterogastric reflux and bile reflux oesophagitis, and it is preferred to perform the reconstruction using a Roux loop.
Palliative surgery
In patients suffering from significant symptoms of either obstruction or bleeding, palliative resection is appropriate. A palliative gastrectomy need not be radical and it is sufficient to remove the tumour and reconstruct the gastrointestinal tract. Sometimes it is impossible to resect an obstructing tumour in the distal stomach and other palliative procedures need to be considered, although the prognosis in such patients, even in the short term, is poor. A high gastroenterostomy is a poor operation that very frequently does not allow the stomach to empty adequately and may produce the additional problem of bile reflux. A Roux loop with a wide anastomosis between the stomach and jejunum may be a
better option, although even this may not allow the stomach to empty particularly well. Gastric exclusion and oesophagojejunostomy are practised by some surgeons. For inoperable tumours situated in the cardia, either palliative intubation, stenting oranother form of recanalisation can be used Recanalisation appears to offer better functional results.
Postoperative complications of gastrectomy
Radical gastrectomy is complex major surgery and predictably there are a large number of potential complications. Leakage of the oesophagojejunostomy should be uncommon in experienced hands. When it does occur it can often be managed conservatively as the Roux-en-Y reconstruction means that it is mainly saliva and ingested food that leaks. Some patients may establish a fistula from the wound or drain site and others may need radiologicalor surgically placed drains. It is unclear whether a nasoenteric tube should be used routinely; many surgeons do use such tubes routinely but this is not supported by any evidence base. It
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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