General Information / Anatomy / Function / Statistics

• Curved, muscular, sac-like structure that is an enlargement of the alimentary canal between the esophagus and the small intestine
• Serves as a food reservoir and secretes gastric juices to aid in the digestion and breakdown of foods
• Stomach cancer used to be one of the most common causes of cancer deaths in Canada
• Decreased considerably in the last 50 years and now accounts for less than 3% of all cancers
• Still the third leading cause of cancer deaths in Great Britain, and relatively common in Japan, China, Chile, and Iceland
• Twice as common in men, mainly middle-aged
• About 75% of patients whose cancers are confined to the stomach lining without any spread are potentially curable
• Tends to spread early in its development
• Five year rate falls to 10% among patients with more advanced cancer--most often the case
• Overall the five year cure rate is about 10%, a statistic that hasn't changed in 20 years
• For statistics, click here

Symptoms / Signs

• Mild abdominal pain aggravated by food
• Nausea, vomiting
• Heartburn
• Indigestion
• Loss of appetite
• Difficulty in swallowing
• Gastrointestinal bleeding (40% of cases)
• Vomiting food
• Tarry-looking or black stools
• Extreme fatigue
• Rapid weight loss

Etiology / Carcinogens / Risks

• Those between ages 50 and 59 are at higher risk
• The exact cause is unknown
• Occurs most often among people from lower social and economic classes
• Researchers believe that diet or other environmental factors predispose a person to develop stomach cancer
• Lack of refrigeration and the eating of tainted or decaying food may be a contributing factor
• Consumption of smoked, highly salted and excessive amounts of barbecued foods
• The question of whether nitrates (chemicals that were widely used as preservatives) cause stomach cancer is unresolved. Nitrites today are used only in very minute quantities in food preservation, e.g., bacon etc. No carcinogenic risk is likely at this very low dose.
• Enzymes in the intestinal tract can convert nitrates to nitrites and animal studies have indicated nitrites can be converted into potential carcinogens.
• Patients with pernicious anemia show a predisposition to cancer--(these people are unable to absorb vitamin B12)--are 5 to 10 percent more likely to develop gastric cancer
• Previous stomach surgery for benign ulcers or other disorders seems to increase the risk of cancer 15 or 20 yrs later
• Patients with a type of gastritis marked by atrophy of the tissues that produce gastric acid are at higher risk
• The presence of a Helicobacter pylori infection may lead to stomach inflammation that can induce mutations and DNA damage
• Chronic reflux of bile into the stomach is also linked to a higher incidence
• The cause or mechanism by which these circumstances may promote stomach cancer is unknown
• Risk increases with the use of tobacco and alcohol

Diagnosis / Staging / Grading / Types

• Early diagnosis is essential if treatment is to be successful. Gastroscopy and biopsy of abnormal area is the most accurate diagnostic tool.
• Blood tests for iron deficiency anemia
• Stool examination for occult blood
• Gastric ulcers deserve special attention because a cancer may appear like an ulcer
• Scanning procedures may be carried out to detect metastases

Staging

Staging depends on how deeply the primary tumour has invaded through the stomach wall

Stage 0	in situ tumour
Stage I	involves only the inner layer of the stomach wall, with or without lymph node spread
Stage II	stomach wall and lymph nodes are close to the tumour inner layers with extreme nodal involvement, or full thickness with no nodal involvement
Stage III	tissues adjacent to stomach lymph nodes are close to tumour; extensive wall invovlement with nodal involvement or direct spread to other organs close to tumour; extensive wall involvement or direct organs
Stage IV	tumour directly involves adjacent organs with nodal involvement; or there is very extensive nodal involvement (greater than 15 nodes); or there are distant metastases

• Stomach cancers develop most often in the lower portion closest to the small intestine
• 30% develop in the cardia, near the opening from the esophagus
• 20% develop in the lesser curvature
• 3 to 5% in the greater curvature
• Stomach cancer spreads through the lymphatic systems and blood vessels by direct invasion to adjacent structures and by "seeding"; i.e., new cancers on other surfaces in the abdominal cavity.
• Often has metastasized at the time of initial diagnosis
• Sites of metastases include gastrointestinal organs, lungs, bones, uterus, ovaries, kidneys, brain and skin
  
  Types
  
• About 95% are ulcerated adenocarcinomas
• Remaining cancers are usually a type of lymphoma (gastric lymphoma) or a rare kind of sarcoma (leiomyosarcoma) which may develop from the smooth muscles of the stomach wall. This is now known as a "stromal tumour".
• Cancers growing as a localized mass have a better prognosis than those that infiltrate adjacent tissue

Treatment

Surgery

• Surgery offers the best chance of cure
• Surgery removes most or all of the stomach (subtotal or total gastrectomy) along with the surrounding lymph nodes
• Over 50% of early-stage cases are curable
• Operation entails removal of all or part of the stomach along with the lower esophagus or upper part of the small intestine, depending on site of the tumour
• If cancer has spread, the affected parts of other organs (liver, spleen, pancreas or colon) may also be removed, provided there is no distant metastases
• Esophagojejunostomy is a procedure where the esophagus is connected to the mid-small bowel.  5% of patients may not survive this operation.

Radiation

• Radiation therapy, except for local treatment of bleeding or painful metastases to bones, is of little value
• Radiation is used to relieve symptoms, not to cure cancer
• The amount of radiation needed to eradicate the cancer is greater than the patient can tolerate

Chemotherapy

• Chemotherapy may be of significant, albeit temporary, benefit to patients
• Chemotherapy is used to treat advanced or metastatic disease
• Single anticancer drug has produced a reduction in tumour size in 20% of patients
• A combination of drugs increases the response rate to 30%-35% but average survival is still less than one year
• Adjuvant chemotherapy for patients treatable with surgery is being studied as a preventive measure against metastases, but is experimental
• Post-surgery patients can still eat their favorite foods but should have 6 or 8 small meals rather than 3 large. Some foods may need to be pureed or well cooked for easier digestion.

Revised May 1999