Gastric adenocarcinoma - Gastrointestinal oncology

Gastric adenocarcinoma

Definition

Malignant tumour of the stomach.

Incidence

10 per 10,000 per year, accounts for 10% of cancer deaths due to late presentation.

Age

More than 30 years. Incidence rises above age 50 years.

Sex

2M > 1F

Geography

Highest in Japan and Chile.

Aetiology

Pre-malignant conditions include chronic atrophic gastritis with intestinal metaplasia and adenomatous polyps of the stomach.

·        H. pylori causes atrophic gastritis resulting in dysplasia and neoplasia.

·        Dietary carcinogens possibly including nitrates and alcohol. Salt may be involved.

Pathophysiology

Gastric adenocarcinomas are derived from mucus secreting epithelial cells most occurring in the antrum. Tumours may be of three types:

·        Ulcerating (most common) with appearance similar to benign ulcers but with raised edges and no normal mucosa.

·        Polypoidal which often bleed leading to earlier pre-sentation.

·        Infiltrating when fibrous tissue causes a firm non-distendable or linitis plastica (leather bottle) stomach. It tends to present late with non-specific symptoms.

Spread may be direct invasion to the liver and pancreas, transcoelomic spread resulting in a malignant ascites and ovarian Krukenberg tumour, lymphatic spread to regional and distant lymph nodes (Virkow’s node) and via the portal circulation to the liver.

Clinical features

Patients tend to present late with non-specific weight loss, anorexia and anaemia. There may be dyspepsia or haematemesis. In early stages there may be occult blood in faeces. Examination reveals epigastric tenderness and often a mass. Dermatomyositis and acanthosis nigricans may be manifestations of an underlying gastric malignancy.

Microscopy

Histologically gastric adenocarcinomas may have an intestinal pattern with gland like spaces or they may be diffuse infiltrative carcinoma with sheets of anaplastic cells which have a mucin containing vacuole.

Investigations

Diagnostic testing usually involves an endoscopy and biopsy, which may be preceded by a barium meal. If there is an associated ascites diagnostic tapping and cytological examination may be useful. Anaemia is a non-specific finding and liver metastases may cause a rise in liver function tests. A CT scan is used for staging and surgical planning.

Management

Treatment of choice is surgical resection wherever possible. At laparotomy if there is no evidence of local invasion or spread beyond local nodes, a partial gastrectomy is performed for distal carcinoma (Bilroth II with anastomosis to the jejunum and closure of the duodenal stump) or in proximal carcinomas a total gastrectomy is performed. Lymph node clearance is performed of regional nodes. Palliative resections may be performed for blood loss or obstruction. Combination chemotherapy may be used in disease not amenable to surgery.

Prognosis

In Japan early disease cure rates are up to 90%. Overall 5-year survival in the United Kingdom is around 10% due to late presentation.