Stomach cancer, also known as gastric cancer, is the accumulation of an abnormal (malignant, cancerous) group of cells that form a mass in a part of the stomach.
According to the World Health Organization, 723,000 cancer-related deaths are caused by stomach cancer each year, globally. It is the fifth most common cancer worldwide, but the third leading cause of cancer-related deaths.
In the United States, there are approximately 25,500 new cases of stomach cancer, annually - it represents 2 percent of all new cancers diagnosed in the country.
The majority of people diagnosed with stomach cancer either already have metastasis or eventually develop it. Metastasis is when the cancer spreads from the area where it first developed.
Around 90-95 percent of all stomach cancers are a type referred to as adenocarcinoma of the stomach. In this version, the cancer develops from the cells that form the mucosa, the most superficial lining of the stomach that produces mucus.
Here are some key points about stomach cancer. More detail and supporting information is in the main article.
Symptoms of stomach cancer
There are approximately 25,500 new cases of stomach cancer in the US every year
There are several symptoms associated with stomach cancer. However, as they also exist in many other much less serious conditions, gastric cancer may be difficult to recognize initially. It is for this 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 (or 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)
The following 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 following: unexpected weight loss, being sick or anemia (patient usually feels tired and possibly out of breath)
According to the NHS (National Health Service), United Kingdom, 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 also see a doctor:
- A close relative who has/had stomach cancer
- Barret's esophagus
- Dysplasia - abnormal collection of cells; these are typically a precancerous form of cells
- Gastritis - inflammation of the lining of the stomach
- Pernicious anemia - the stomach does not absorb vitamin B12 properly from food
- History of 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 for stomach cancer
Risk factors linked to stomach cancer include:
- Certain medical conditions - including esophagitis, GERD (gastroesophageal reflux disease), peptic stomach ulcer, Barrett's esophagus, chronic gastritis, stomach polyps.
- Smoking - regular, long-term smokers have twice the risk of developing stomach cancer compared to non-smokers.
- Helicobacter pylori infection - this bacterium is harmless for most people. However, it can cause infection and stomach ulcers in some individuals. Chronic ulcers pose some risk in the development of gastric cancer
- Family history - having a close relative who has/had stomach cancer.
- Consuming foods which contain aflatoxin fungus - these may occur in crude vegetable oils, cocoa beans, tree nuts, groundnuts, figs and other dried foods, and spices.
- Diet - people who regularly eat salted fish, salty foods, smoked meats, and pickled vegetables have a higher risk of developing gastric cancer.
- Age - the risk of developing stomach cancer increases significantly after the age of 55.
- Sex - men have twice the risk of developing stomach cancer compared with women.
- Previous or existing cancers - patients who have/had esophagus cancer or non-Hodgkin's lymphoma are more likely to develop stomach cancer. Men who have/had prostate, bladder, or testicular cancer are at higher risk, as are females who have/had cervical, ovarian, or breast cancer.
- Some surgical procedures - especially surgery to the stomach or a part of the body that affects the stomach, like the vagus nerve.
Causes of stomach cancer
Cancer starts off when the structure of DNA changes. When this happens, it can disrupt the instructions that control cell growth.
Cells that should die may not do so, and cells that should be newly created may be produced too rapidly, or in an uncontrollable way.
Experts are not sure why some stomach cells mutate and become cancerous. Why only a few people develop stomach cancer is still a mystery, too.
Diagnosis of stomach cancer
Individuals with some of the signs and symptoms listed above should see their doctor as soon as possible. The physician will ask the patient about the symptoms, family history, possibly some lifestyle characteristics (eating habits), medical history, and carry out a physical examination to check for stomach tenderness or lumpiness.
If the doctor suspects possible stomach cancer, the patient will be referred to a specialist for tests. Diagnostic measures may include:
A specialist can look at the inside of the patient's stomach using a remotely-controlled endoscope.
The specialist looks at the inside of the patient's stomach with a fiber optic camera. Some tissue samples may be taken if the doctor suspects cancer - this is called a biopsy.
If cancer is suspected in the top part of the stomach, the specialist may carry out an ultrasound scan (endoscopic ultrasound).
Barium meal X-ray
In a barium swallow study, the patient swallows a liquid which contains barium; this helps identify the stomach during an X-ray.
The specialist may want to look inside the abdomen in more detail to determine how much the cancer has spread. In a procedure called a laparoscopy, the patient is placed under a general anesthetic, and a laparoscope (a thin tube with a camera at the end) is inserted through a small incision in the lower part of the stomach.
CT scan or PET scan
These scans take a series of radiographic pictures of the inside of the body. The images help the specialist determine how advanced the cancer is, and where in the body it has spread to. These types of scans also help the doctor decide on the most appropriate treatment.
A liver ultrasound scan may be recommended if the doctor thinks that the cancer may have spread to the liver.
Treatments for stomach cancer
Treatment for stomach cancer depends on several factors, including the severity of the cancer and the patient's overall health and preferences.
Treatments may include surgery, chemotherapy, radiation therapy, medications, and taking part in clinical trials.
The surgeon's aim is to remove the stomach cancer from the body as well as a margin of healthy tissue (necessary to make sure no cancerous cells are left behind). Examples include:
- Taking out tumors from the stomach lining in early stage cancer - the surgeon will use endoscopy to remove very small tumors that are confined to the inside lining of the stomach - this is called endoscopic mucosal resection
- Subtotal gastrectomy - a part of the stomach is surgically removed
- Total gastrectomy - the whole stomach is surgically removed
Abdominal surgeries are significant procedures and may require prolonged recovery time. Patients may have to stay in hospital for 2 weeks after the procedure. This will be followed by several weeks of recovery at home.
Radiation therapy (radiotherapy)
In radiotherapy, energy rays are used to target and kill cancerous cells. Radiotherapy is not commonly used for the treatment of stomach cancer because of the risk of harming other nearby organs. However, if the cancer is advanced and/or causing serious symptoms like bleeding or severe pain, radiotherapy is an option.
Neoadjuvant radiation refers to the use of radiation therapy before surgery to make the tumors smaller so that they can be removed more easily.
Adjuvant radiation is radiation therapy used after surgery. The aim is to kill off any remaining cancer cells around the stomach.
Patients may experience indigestion, nausea, vomiting, and diarrhea as a consequence of undergoing radiation therapy.
Chemotherapy is a specialist treatment that uses drugs to stop rapidly-growing cancer cells from dividing and multiplying. These drugs are known as cytotoxic medicines. The medication travels throughout the patient's body and attacks cancer cells at the primary site of the cancer and any other regions it has metastasized to.
Neoadjuvant chemotherapy is administered before surgery to shrink the tumor so that it can be surgically removed more easily.
Adjuvant chemotherapy is administered after surgery to destroy any cancerous cells that may have remained behind. Chemotherapy may be the preferred treatment modality for certain types of gastric cancer, including gastrointestinal stromal tumors and gastric lymphoma.
Examples of targeted medications include Sutent (sunitinib) and Gleevec (imatinib), which attack specific types of abnormalities in cancerous cells for patients with gastrointestinal stromal tumors.
These are experimental therapies which may be trying out new drugs or using existing therapies in novel ways. Patients may want to take part in some of the latest treatments. It is important to remember that clinical trials are experimental and in no way guarantee a cure for stomach cancer.
Patients should discuss this option carefully with their doctors and family and bear in mind that such therapies have many unknowns, for example, the investigators may not be sure what side effects the participants might experience.
Can stomach cancer be prevented?
Experts do not know exactly what causes stomach cancer, and there are no vaccines against it. Therefore, there is really no way to effectively prevent it.
However, steps can be taken to reduce the risk of developing the disease; these include:
- Fruit and vegetables - people who eat plenty of fruit and vegetables are usually less likely to develop stomach cancer, compared with those who don't.
- Eat less salty and smoked foods.
- Smoking - if you smoke, quit. If you don't smoke, do not take it up.
- Check with a doctor - individuals can ask whether they have any medical conditions that might increase the risk of developing stomach cancer. Those who do might consider having periodic screening.