Gastric cancer

There are 700,000 new cases of gastric cancer worldwide each year.

Epidemiology

• overall incidence is decreasing, but incidence of tumours arising from the cardia is increasing
• peak age = 70-80 years
• more common in Japan, China, Finland and Colombia than the West
• more common in males, 2:1

Histology

• signet ring cells may be seen in gastric cancer. They contain a large vacuole of mucin which displaces the nucleus to one side. Higher numbers of signet ring cells are associated with a worse prognosis

Associations

• H. pylori infection
• blood group A: gAstric cAncer
• gastric adenomatous polyps
• pernicious anaemia
• smoking
• diet: salty, spicy, nitrates
• may be negatively associated with duodenal ulcer

Investigation

• diagnosis: endoscopy with biopsy
• staging: CT or endoscopic ultrasound - endoscopic ultrasound has recently been shown to be superior to CT

Surgical aspects

There is some evidence of support a stepwise progression of the disease through intestinal metaplasia progressing to atrophic gastritis and subsequent dysplasia, through to cancer. The favoured staging system is TNM. The risk of lymph node involvement is related to size and depth of invasion; early cancers confined to submucosa have a 20% incidence of lymph node metastasis. Tumours of the gastro-oesophageal junction are classified as below:




Staging

• CT scanning of the chest abdomen and pelvis is the routine first line staging investigation in most centres.
• Laparoscopy to identify occult peritoneal disease
• PET CT (particularly for junctional tumours)

Treatment

• Proximally sited disease greater than 5-10cm from the OG junction may be treated by sub total gastrectomy
• Total gastrectomy if tumour is <5cm from OG junction
• For type 2 junctional tumours (extending into oesophagus) oesophagogastrectomy is usual
• Endoscopic sub mucosal resection may play a role in early gastric cancer confined to the mucosa and perhaps the sub mucosa (this is debated)
• Lymphadenectomy should be performed. A D2 lymphadenectomy is widely advocated by the Japanese, the survival advantages of extended lymphadenectomy have been debated. However, the overall recommendation is that a D2 nodal dissection be undertaken.
• Most patients will receive chemotherapy either pre or post operatively.

Prognosis

UK Data