Gastric cancer

Gastric cancer The incidence of carcinoma of the distal stomach is decreasing. In contrast, there appears to be an increase in the incidence of carcinoma in the proximal stomach, particularly the oesophagogastric junction. Carcinoma of the distal stomach and body of the stomach is most common in low socioeconomic groups, whereas the proximal gastric cancer seems to affect principally higher socioeconomic groups. Proximal gastric cancer does not seem to be associated with H. pylori infection, in contrast with carcinoma of the body and distal stomach

Aetiology Pernicious anaemia Gastric atrophy Gastric polyps. Patients who have had peptic ulcer surgery. Duodenogastric reflux and reflux gastritis. Intestinal metaplasia Cigarette smoking. Diet appears to be important. Excessive salt intake, deficiency of antioxidants and exposure to N-nitroso compounds.

CLINICAL FEATURES In advanced cancer, early satiety, anorexia, bloating, distension, nausea and vomiting may occur. The tumour frequently bleeds, resulting coffee ground vomiting and iron deficiency anaemia. Pallor, wt. Loss, weakness, malaise. Obstruction leads to dysphagia. With pyloric involvement the presentation may be of gastric outlet obstruction. Epigastric mass in 25% and hepatomegaly in 10% Supraclavicular node, blumer shelf, Krukenberg tumor. Non-metastatic effects of malignancy are seen, particularly thrombophlebitis (Trousseau’s sign) and deep venous thrombosis.

Pathology Lauren classification. In intestinal gastric cancer, the tumour resembles a carcinoma 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 spreads widely in the gastric wall, this has a much worse prognosis. A small proportion of gastric cancers are of mixed morphology.

investigations Laboratory Findings Anemia is present in 40% of patients. Carcinoembryonic antigen (CEA) levels are elevated in 65%, usually indicating extensive spread of the tumor. Imaging Studies An upper gastrointestinal series is diagnostic for tumors. Major diagnostic problems are posed by ulcerating tumors, a few of which may not be distinguishable radiologically from benign peptic ulcers. Large gastric carcinomas can usually be identified as such by their gross appearance at endoscopy. All gastric lesions, whether polypoid or ulcerating, should be examined by taking multiple biopsy and brush cytology specimens during endoscopy

Spread of carcinoma of the stomach 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, the tumour even appearing in the supraclavicular nodes (Troisier’s sign). Blood-borne metastases These occur first to the liver and subsequently to other organs, including lung and bone. Transperitoneal spread This is a common mode of spread once the tumour has reached the serosa of the stomach and indicates incurability

Surgical treatment Total gastrectomy The stomach is removed en bloc, including the tissues of the entire greater omentum and lesser omentum. Subtotal gastrectomy For tumours distally placed in the stomach, it appears unnecessary to remove the whole stomach.

Other treatment modalities Radiotherapy The routine use of radiotherapy is controversial. Radiotherapy has a role in the palliative treatment of painful bony metastases. Chemotherapy Gastric cancer may respond well to combination cytotoxic chemotherapy, to improve the outcome following surgery. The best results are currently obtained using a combination of epirubacin, cis-platinum and infusional 5-FU.

GASTROINTESTINAL STROMAL TUMOURS Gastrointestinal stromal tumours (GIST) may arise in any part of the gastrointestinal tract but 50 per cent will be found in the stomach. Previously named leiomyoma and leiomyosarcoma. Peritoneal and liver metastases are most common, but spread to lymph nodes extremely rare.

CLINICAL FEATURES The only ways that many stromal tumours are recognised are either that the mucosa overlying the tumour ulcerates leading to bleeding, or that they are noticed incidentally at endoscopy. Tumours over 5 cm in diameter should be considered to have metastatic potential. Surgery is the primary mode of treatment. Smaller tumours can be treated by wedge excision.

Larger tumours may require a gastrectomy or duodenectomy Larger tumours may require a gastrectomy or duodenectomy. Larger multiple tumours which require multivisceral resection may be better treated with three to six months of imatinib prior to operation as this will usually radically reduce the size and vascularity of the tumours.

GASTRIC LYMPHOMA Unlike gastric carcinoma, the incidence of lymphoma seems to be increasing. It accounts for 5 per cent of all gastric neoplasms. The common symptoms being pain, weight loss and bleeding. Acute presentations of gastric lymphoma, such as haematemesis, perforation or obstruction, are not common.

Diagnosis is made as a result of the endoscopic biopsy Diagnosis is made as a result of the endoscopic biopsy. Following diagnosis, adequate staging is necessary, primarily to establish whether the lesion is a primary gastric lymphoma or part of a more generalised process. CT scans of the chest and abdomen and bone marrow aspirate are required, as well as a full blood count. Treatment by surgery. Chemotherapy alone is appropriate for patients with systemic disease.

DUODENAL TUMOURS Benign duodenal tumours Duodenal villous adenomas occur principally in the periampullary region. They are often found in patients with familial adenomatous polyposis. They have malignant potential, they should be locally excised with histologically clear margins.

Duodenal adenocarcinoma Although uncommon, this is the most common site for adenocarcinoma arising in the small bowel. Most tumours originate in the periampullary region and commonly arise in pre-existing villous adenomas. Patients present with anaemia or obstruction of the duodenum. Direct involvement in the ampulla leads to obstructive jaundice. Curative surgical treatment by pancreaticoduodenectomy.

Neuroendocrine tumours A number of neuroendocrine neoplasms occurs in the duodenum. It is a common site for primary gastrinoma (Zollinger–Ellison syndrome). Non-functioning neuroendocrine tumours (usually called carcinoid tumours)

Zollinger–Ellison syndrome This syndrome is mentioned here because the gastrin-producing endocrine tumour is often found in the duodenal loop, although it also occurs in the pancreas, especially the head. It is a cause of persistent peptic ulceration. The patient had a very high basal acid output, as the parietal cell mass was already nearly maximally stimulated by pathological levels of gastrin. The advent of proton pump inhibitors such as omeprazole has rendered this extreme endocrine condition fully controllable.

DUODENAL OBSTRUCTION Duodenal obstruction in the adult is usually due to malignancy, and cancer of the pancreas is the most common cause. Treatment: is usually by gastroenterostomy but duodenal stenting is increasingly being used. A variety of other malignancies can cause duodenal obstruction, including metastases from colorectal and gastric cancer. Obstruction usually follows an attack of pancreatitis and, on occasions, the obstruction may be mistaken for malignancy.

Acute gastric dilatation This condition usually occurs in association with pyloroduodenal disorders or postsurgery without nasogastric suction. The stomach, which may be atonic, dilates enormously. Often the patient is also dehydrated and has electrolyte disturbances. Failure to treat this condition can result in a sudden massive vomit with aspiration into the lungs. The treatment is nasogastric suction, with a large-bore tube, fluid replacement and treatment of the underlying condition.