Interpretación de resultados (orientado a un análisis de competitividad)

Christopher Lattimer, Simon Gibbs

Nearly all gastric cancers detected in the UK are advanced adenocarcinomas with an appalling overall 5-year survival rate of 5–10%. In comparison, in Japan, where the disease is commonest, over 30% of all gastric cancers are detected early and the overall 5-year survival rates exceed 50%. Japanese experience in mass screening, appreciation of the more radical D2 gastrectomy and different disease behaviour patterns all contribute to improved survival.

Demography

The incidence of gastric cancer has fallen dramatically in the Western world over the past 30 years. Gastric cancer is twice as common in males, peaks in incidence between 55 and 65 years, is associated with blood group A and Helicobacter pylori and occurs more frequently amongst the lower social classes. There is a genetic link as stomach cancer can run in families, but environmental factors such as diet and methods of food preservation are also important.

Types

Gastric cancer can be divided into intestinal and diffuse types. The intestinal type matches geographical areas of increased incidence and is usually accompanied by an area of chronic gastritis. The diffuse type bears no such relationship.

Risk factors

Chronic gastritis, gastric ulcers and gastric polyps are lesions often considered precancerous. The gastric remnant following a partial gastrectomy for benign disease has an increased risk of developing a gastric carcinoma. Autoimmune gastritis (pernicious anaemia) is subject to dysplastic change which may then become neoplastic. Populations where gastric cancer is common have a high incidence of chronic gastritis, mucosal atrophy and subsequent intestinal metaplasia, all of which are associated with H. pylori.

Over 90% of carcinomas are found in areas of gastritis and 10% of patients with chronic gastritis develop a carcinoma. Gastric adenomatous polyps are considered premalignant, and the larger the polyp the higher the incidence of malignancy. There is no convincing evidence that chronic gastric ulcers undergo malignant change, but any gastric ulcer should be biopsied.

Presentation

Clinical presentation depends upon lesion site and disease advancement. The commoner antral lesions may cause outlet obstruction with vomiting and a succussion splash or fistulate into the colon. Cardiac lesions may cause dysphagia or regurgitation. Fundal lesions are often silent, with anorexia and increasing satiety after meal times. Irrespective of site, many first present with indigestion pains and dyspepsia. Carcinomas may perforate, ulcerate causing anaemia and lead to ill health with weakness and weight loss. A knobbly liver or the carcinoma itself may be palpable. A left supraclavicular node mass (Virchow’s node) (Troisier’s sign) or ascites indicates advanced disease. Jaundice may be caused by nodal compression at the porta hepatis, direct ductal involvement or by progressive liver replacement.

Diagnosis

The mainstay of diagnosis for early lesions is to perform an upper GI endoscopy on all patients with a recent onset of dyspepsia or indigestion-like pains. All suspicious lesions and unusual areas of gastritis should be biopsied or undergo brush cytology. Linitis plastica (leather bottle stomach) is suggested if the stomach fails to distend on insufflation. Repeat biopsies at the same site (trench biopsy) may be required to reach the areas of submucosal infiltration that are typical for these carcinomas. Double contrast barium radiology is complementary to diagnosis. A filling defect, mucosal irregularity or stricture maybe visualized.

Staging

Ultrasound and CT scan allow visualization of distant metastases in the liver and lungs, which normally precludes surgery. Endoscopic ultrasound should be performed for all patients in whom surgery is considered. The ultrasound probe is located in the end of an ‘end viewing’ endoscope, and is passed like a normal gastroscope to the level of the tumour. It generates a radial ultrasonic image thus allowing T and N staging, permitting a much more accurate assessment of local operability. Laparoscopy allows exclusion of small peritoneal deposits or small metastases and allows cytology and biopsy of any suspicious lesions. Enlarged lymph nodes can also be seen. The lesser sac can sometimes be entered safely and any posterior extension into the pancreas can be visualized. Accurate staging of the disease helps prevent unnecessary laparotomy, although the presence of involved nodes does not always preclude surgery.

Preoperative nutrition

Many patients who present with a gastric carcinoma are malnourished. If oral feeds can be tolerated and there is no obstruction then high calorie and protein supplemented liquid feeds can be given under the guidance of an experienced dietitian, prior to surgery. If oral feeding is not possible, then a radiologically placed nasojejunal tube may be useful. In obstructed lesions TPN can be used prior to surgery but this should be replaced by a jejunal feeding route created at surgery. In severely cachectic patients, operation may need to be delayed to allow correction of profound nutritional disability.

The D2 gastrectomy

The D2 gastrectomy has been shown to increase survival in gastric cancer patients in Japanese series. All the lymph node groups which drain the stomach are classified according to their site (supra/infra pyloric, right/left cardiac, greater/lesser curve and those groups along and at the origins of the arterial supply to the stomach). The primary tumour is documented in the upper, middle or lower third of the stomach. N1 nodes are situated within 3 cm of the primary. N2 nodes are all those mentioned above greater than 3 cm from the primary. N2 nodes could all become N1 nodes if the tumour was sited in a different region. A D2 resection involves removing all the N1 and N2 nodes with a 5 cm clearance of the tumour. The operative mortality for a D2 gastrectomy should not exceed 5%. Although there are undoubtedly some patients who would benefit from having a D2 resection rather than a D1 (those with disease that has just started to spread to the N2 nodes), there is as yet no convincing European data that this type of resection increases overall 5 year survival if performed routinely for all patients undergoing surgery for gastric cancer. It is hoped that with more accurate staging, patients who would benefit from D2 type resection will be identified pre-operatively and their operation tailored accordingly.

Anastomosis

Gastrointestinal continuity is restored after a radical lower partial gastrectomy with a Roux-en-Y anastomosis. Bilroth 1 gastrectomy is considered ill advised because the anastomosis will be sited on the original tumour bed. Continuity after total gastrectomy is established by Roux-en-Y loop. A naso-jejunal tube is placed allowing aspiration of the gastric remnant or oesophagus, and enteral feeding via the jejunum. Once a contrast swallow shows integrity at 7 days, oral feeding can be started.

Palliative surgery

With better preoperative staging less palliative resections are now performed. Most patients, particularly the elderly, will not benefit from surgery if there is no chance of complete resection. In younger patients with longer life expectancy, resection may still be

appropriate to debulk the disease prior to other palliative treatments. If patients have gastric obstruction however (such as in pyloric stenosis), a gastrojejunostomy is indicated to divert the gastric contents directly into the jejunum.

Post-gastrectomy symptoms

Gastrectomy is associated with post-gastrectomy symptoms in 20% of cases. These include diarrhoea, osmotic (early) and hypoglycaemic (late) dumping, anaemia and malnutrition. Mild dumping usually responds to simple dietary manipulation and an experienced dietitian should be consulted. If dumping is severe and fails to settle, it can be treated with anti-peristaltic segments which can be fashioned surgically to hold up emptying into the jejunum. Roux-en-Y construction with an anastomosis at least 50 cm distal to the upper resection limit eliminates biliary reflux, which dogged patients who had Polya or Bilroth I gastrectomies. Vitamin B12 injections may be needed in total

gastrectomy patients, who fail to secrete intrinsic factor.

Prognosis

Disease stage is the best prognostic indicator. Well-differentiated lesions carry a better prognosis than the poorly differentiated or signet cell types. Vascular invasion is associated with future liver metastasis. Serosal invasion, perforation and poor differentiation are associated with peritoneal dissemination. Lymph node metastases are associated with both. Upper gastric lesions are often advanced with a poor prognosis. There is no convincing evidence that chemotherapy or radiotherapy prolongs survival.

Lymphoma

Gastric lymphoma is the commonest extranodal primary site for non-Hodgkin’s lymphoma, and is strongly associated with H. pylori. Most are B-cell lymphomas arising from mucosa-associated lymphoid tissue (MALT). They present similarly to gastric carcinomas. Therapy depends on stage and involves resection and adjuvant chemotherapy for early stage lesions (Ann Arbor stage I, II), chemotherapy and/or radiotherapy for advanced stages (III, IV). Some early low-grade MALT lymphomas respond to Helicobacter eradication therapy alone. Careful observation is required if chemotherapy or radiotherapy is initiated in advanced lesions, as perforation may occur.

Carcinoid tumour

Carcinoid tumours usually form a polypoidal mass in the body or fundus. The carcinoid syndrome of flushing, diarrhoea and bronchospasm occurs when liver metastases secrete large amounts of 5-hydroxytryptamine (serotonin, 5-HT), but in many cases of gastric carcinoid 5-hydroxytryptophan and histamine are released rather than 5-HT, leading to

atypical skin blotches rather than whole body flushes. Resection is the mainstay of treatment and offers 5-year survival rates of over 75%. Chemotherapy has also been employed in those not fit or too advanced for surgery.

GI stromal tumours (GIST)

Gastric leiomyomas and leiomyosarcomas most often present with bleeding due to ulceration. Malignant diagnosis depends on the number of mitoses present and whether the lesion recurs! Resection offers 5-year survival rates approaching 50%.

Further reading

McCulloch P. Description of the Japanese method of radical gastrectomy. Annals of the Royal

College of Surgery of England, 1994; 76:110–114.

Raines SA. Surgery for cancer of the stomach. In: Griffin SM, Raines SA (eds) Upper

Gastrointestinal Surgery—A Companion to Specialist Surgical Practice. W.B. Saunders,

London, 1999; 145–190.

Siewert JR et al. Benefits of D2 lymph node dissection for patients with gastric cancer and pN0 pN1 lymph node metastases. British Journal of Surgery, 1996; 83:1144–1147.

Related topics of interest

Nutrition in the surgical patient (p. 233); Oesophageal cancer (p. 237).