Stomach cancer, also known as gastric cancer, is the accumulation of an abnormal (malignant, cancerous) group of cells that form a tumor in any part of the stomach.
In most cases it refers to cancer that starts off in the mucus-producing cells on the lining of the inside of the stomach (adenocarcinoma).
According to the World Health Organization, 800,000 cancer-related deaths are caused by stomach cancer each year globally. It is the fourth most common cancer worldwide, but the second leading cause of cancer-related deaths in the world.
Gastric cancer is more common among males, and people in developing nations compared to industrialized countries, the exception being Japan and South Korea, where the disease is much more common than in the USA, Canada or Europe.
In the United States, there are approximately 25,500 new cases of stomach cancer annually - it represents 2% of all new cancer diagnoses in the country, compared to 20.8% in South Korea.
There are approximately 25,500 new cases of stomach cancer in the US every year
The majority (80%-90%) of people diagnosed with stomach cancer either already have metastasis or eventually develop it. Metastasis is when the cancer spreads beyond its site of origin, to other parts of the body.
Napoleon Bonaparte probably died of stomach cancer, researchers from the USA, Switzerland and Canada concluded after examining historical evidence.
Contents of this article:
Types of stomach cancer
There are several types of stomach cancers. These include:
1) Adenocarcinoma of the stomach
Between 90% and 95% of all stomach cancers are of this type. The cancer develops from the cells that form the mucosa, the innermost lining of the stomach.
2) Lymphoma of the stomach
Lymphoma of the stomach accounts for 4% of stomach cancers. Cancerous cells form in the immune tissue (lymphatic tissue) that is sometimes found in the wall of the stomach. Lymphatic tissue drains away fluid and helps fight infection.
3) Gastrointestinal stromal tumor (GIST)
Gastrointestinal stromal tumors form in the muscle or connective tissue of the stomach wall (interstitial cells of Cajal). Some of these tumors may be benign (non-cancerous). GISTs can also be found in other parts of the digestive tract.
4) Neuroendocrine tumors
The cancerous cells collect and form tumors in the hormone-making cells, usually in the digestive tract (including the stomach). This type of stomach cancer is rare; the most common is carcinoid tumor.
Other types of stomach cancer
Other types of very rare cancer of the stomach include, squamous cell carcinoma, leiomyosarcoma, and small cell carcinoma.
Symptoms of stomach cancer
A symptom is something the patient feels and describes, such as a stomachache, while a sign is something others, including doctors and nurses can detect, such as a rash.
There are several symptoms associated with stomach cancer. However, as they also exist in many other much less serious conditions and illnesses, gastric cancer may be difficult to recognize initially.
It is for that reason that so many patients are not diagnosed until the disease is already well advanced.
Early symptoms of stomach cancer may include:
- A sensation of being very full (and rapidly full) during meals
- Dysphagia (swallowing difficulties)
- Feeling bloated after meals
- Frequent burping
- Indigestion that does not go away
- Stomachache, or pain in the sternum (breastbone)
- Trapped wind
- Vomiting (may contain blood).
According to the UK Department of Health, the following alarm signs and symptoms in people at increased risk of developing stomach cancer should be taken seriously (see a doctor):
- Indigestion in combination with at least one of the symptoms/signs of unexpected weight loss, being sick or anemia (patient usually feels tired and possibly out of breath).
According to the NHS (National Health Service), UK, people aged 55+ years who develop persistent indigestion should see their doctor.
Individuals who develop indigestion and have at least one of the following in their medical history should see a doctor:
- A close relative who has/had stomach cancer
- Barret's esophagus
- Dysplasia - abnormal collection of cells. They are not cancerous but could become cancerous eventually
- Gastritis - inflammation of the lining of the stomach
- Pernicious anemia - the stomach does not absorb vitamin B12 properly from food
- You have undergone previous surgery for stomach ulcers.
When the stomach cancer becomes more advanced, the following signs and symptoms typically become more apparent:
- Accumulation of fluid in the stomach - stomach feels "lumpy"
- Black stools, or blood in stools
- Loss of appetite
- Weight loss.
Risk factors associated with stomach cancer
A risk factor is a condition, disease, lifestyle, or situation which increases the risk of developing a disease or condition. For example, a risk factor for type 2 diabetes is being obese, i.e. obese people have a higher risk of developing diabetes.
Risk factors linked to stomach cancer include:
1) Having certain medical conditions
These include conditions such as Esophagitis, GERD (gastroesophageal reflux disease), Peptic stomach ulcer, Barrett's esophagus, Chronic gastritis, Stomach polyps.
According to the UK's National Health Service, regular long-term smokers have one-and-a-half times the risk of developing stomach cancer compared to lifetime non-smokers.
3) Helicobacter pylori infection
About 50% of the world's population is thought to carry this bacterium. It is harmless for most people. However, it can cause infection and cause stomach ulcers in some individuals, as well as recurring episodes of indigestion or atrophic gastritis (chronic inflammation of the stomach lining). Patients with severe atrophic gastritis have the highest risk of eventually developing gastric cancer (even in such cases, the risk is still relatively small).
4) Family history
Having a close relative who has/had stomach cancer. In about 2% of stomach cancer cases, patients share a genetic mutation in the E-cadherin gene. People with blood type A also have a higher risk - we inherit our blood type from one of our parents.
5) Consuming foods which contain aflatoxin fungus
These may occur in crude vegetable oils, cocoa beans, treenuts, groundnuts, figs and other dried foods, and spices.
People who regularly eat salted fish, salty foods, smoked meats, and pickled vegetables have a higher risk of developing gastric cancer. In Japan and South Korea such foods are popular. The World Cancer Research Fund reported that if people in the UK reduced their salt intake to the recommended daily amount, 1 in every 7 stomach cancer cases could be prevented.
The risk of developing stomach cancer increases significantly after the age of 55 years. In the USA, Canada and Western Europe, the average age of diagnosis is about 70.
Men have twice the risk of developing stomach cancer compared to women. Scientists from MIT said that estrogen protects women from the gastric inflammation that can lead to cancer.
9) Already having or having had another type of cancer
Patients who have/had esophagus cancer or non-Hodgkin's lymphoma are more likely to eventually develop stomach cancer. Men who have/had prostate, bladder or testicular cancer are at higher risk, as do females who have/had cervical, ovarian or breast cancer.
10) Some surgical procedures
Some surgical procedures, especially surgery to the stomach or a part of the body that affects the stomach, can increase the risk of gastric cancer. Examples include partial gastrectomy (when part of the stomach is removed), surgery to remove part of the vagus nerve, or surgery to treat a stomach ulcer.
On the next page we look at the causes of stomach cancer, the stages of stomach cancer and how it is diagnosed. On the final page we discuss available treatments and lifestyle changes that can help you reduce your risk of developing stomach cancer.