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.
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. Approximately 65% of patients diagnosed with early-stage stomach cancer survive more than six months, while for those diagnosed in late stages only 15% survive beyond six months.
Napoleon Bonaparte probably died of stomach cancer, researchers from the USA, Switzerland and Canada concluded after examining historical evidence. They published their findings in Nature clinical Practice Gastroenterology & Hepatology (January 2007 issue).
Types of stomach cancer
There are several types of stomach cancers, including:
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.
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.
Gastrointestinal stromal tumor (GIST) - rare tumors that 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.
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 very rare cancer of the stomach include, squamous cell carcinoma, leiomyosarcoma, and small cell carcinoma.
What are the signs and 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. That is why so many patients are not diagnosed until the disease is already advanced.
Some of the early stomach cancer symptoms may include:
A sensation of being very full (and rapidly full) during meals
Dysphagia (swallowing difficulties)
Feeling bloated after meals
Indigestion that does not go away
Stomachache, or pain in the sternum (breastbone)
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 listed below:
- unexpected weight loss
- being sick
- 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
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
What are the 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.
The risk factors linked to stomach cancer include:
Smoking - 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
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)
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.
Consuming foods which contain aflatoxin fungus. These may occur in crude vegetable oils, cocoa beans, treenuts, groundnuts, figs and other dried foods, and spices.
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.
Some surgical procedures - particularly 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.
What are the causes of stomach cancer?
Cancer starts off when the structure of DNA changes. DNA provides the cells in our body with a basic set of instructions, a bit like a computer program, such as when to reproduce, grow, etc.
When the DNA structure changes, also known as a mutation, it can mess up the instructions that control the growth of cells. Cells that should die may not do so, and cells that should be newly created may be produced too rapidly - in other words, cells reproduce in an uncontrollable way. There is an accumulation of too many cells, i.e. a tumor.
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.
How does stomach cancer metastasize (spread)?
When stomach cancer spreads - when it metastasizes - it will do so in one of three ways:
In the blood - in such cases the cancer spreads into the liver
Through the lymphatic system - the lymphatic system is a series of nodes (glands) located at various points in the body. The lymphatic system is a kind of parallel circulatory system to the circulation of blood (but without a heart as a pump). The nodes produce cells that fight off infection
Directly - stomach cancer can spread directly out of the stomach and into surrounding tissues and/or organs, such as the small intestine, colon or pancreas
How is stomach cancer diagnosed?
People with some of the signs and symptoms listed above should see their doctor as soon as possible. In most cases, the first visit is to a primary care physician (general practitioner, GP). 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 primary care physician suspects possible stomach cancer, the patient will be referred to a specialist for tests. As stomach cancer requires prompt and early treatment, the referral needs to be done as soon as possible.
The stomach specialist, a gastroenterologist, will probably order the following diagnostic tests:
A doctor taking a biopsy using a remotely-controlled endoscope. He monitors his actions by looking through a microscope-like eyepiece
Gastroscopic exam - the specialist looks at the inside of the patient's stomach with a fiber optic camera. The instrument is called an endoscope - a long, thin, flexible tube with a camera at the end. The procedure, which lasts about 15 minutes, is called an endoscopy. The patient will be asked to fast (not eat or drink) for between four to eight hours beforehand, to make sure that the duodenum and the stomach are empty.
In the majority of cases, the patient remains awake during the whole procedure. A sedative may be injected. Some patients may have a local anesthetic sprayed onto the back of their throat.
The endoscope goes down the patient's throat and into his/her stomach so that the doctor can have a good look for signs of cancer, stomach ulcers, and anything unusual. Some tissue samples may be taken if the doctor suspects cancer - this is called a biopsy. The sample is examined in the laboratory to determine whether there are any malignant (cancerous) cells. Non-cancerous cells are called benign.
It usually takes at least one week before the test results come back.
Ultrasound scan - if cancer is suspected in the top part of the stomach, the specialist may carry out an ultrasound scan (endoscopic ultrasound). The scan helps determine the stage of the cancer.
Barium meal X-ray (barium swallow) - the patient swallows a liquid which contains barium. Barium helps the stomach show up during an X-ray. The patient will have to fast for at least six hours before the procedure. The procedure takes approximately 15 minutes.
Staging of stomach cancer
The Stage describes how much the cancer has spread when diagnosis is confirmed. The Grade describes how aggressive the cancer is (how fast it is spreading).
If a stomach cancer diagnosis is confirmed, the patient may need further tests to determine the stage and grade of the cancer.
Laparoscopy - the specialist may want to look inside in more detail to determine whether and by how much the cancer has spread. In a procedure called a laparoscopy, the patient is placed under a general anesthetic and a laparoscope (thin tube with a camera at the end) is inserted through a small incision in the lower part of the stomach.
CT (comtpuerized tomography) scan or PET (positron emission tomography) scan - these devices take a series of X-ray pictures of the inside of the body and use a computer to put them together, creating a very detailed picture. They 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 best and most appropriate treatment.
A liver ultrasound scan may also be recommended if the doctor thinks that the cancer may have spread to the liver.
Sometimes the cancer stage cannot be accurately determined until the patient undergoes surgery and/or starts treatment.
There are different ways cancers are staged. Below is an example of the staging for adenocarcinoma stomach cancer:
Stage I - the tumor lies within the layer of tissue lining the inside of the stomach. Some cancer cells may have made their way to some nearby lymph nodes.
Stage II - the cancer has spread into the muscles of the stomach wall, as well as to more lymph nodes.
Stage III - the cancer cells may have spread through all the stomach layers, as well as into the lymph nodes. In some cases, the cancer has not spread much in the stomach, but has done so extensive into the lymph nodes.
Stage IV - the cancer has spread well beyond the stomach, into nearby tissue and organs. It could also be a small cancer that has spread much further into distant parts of the body.
Most patients are diagnosed at stage 3 - at this stage a complete cure is extremely rare.
According to the UK's National Health Service, there are three Grades of stomach cancer:
Low grade - a slow-spreading cancer
Medium grade - the cancer spreads faster than a low-grade one
High grade - this is an aggressive cancer that is likely to spread rapidly
What are the treatment options for stomach cancer?
The type of treatment for stomach cancer the doctor may recommend depends on several factors, including the stage of the cancer, the grade of the cancer, and the patient's overall health and preferences.
Treatment options may include surgery, chemotherapy, radiation therapy, medications and taking part in clinical trials.
The surgeon's aim is to surgically remove the stomach cancer from the body as well as a margin of health 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. Obviously, this involves only the part of the stomach with cancer.
Total gastrectomy - the whole stomach is surgically removed. The surgeon then connects the esophagus to the small intestine directly. This option is recommended if a large part of the stomach has cancerous tumors.
To help relieve symptoms - this is performed in patients with advanced cancer to relieve the signs and symptoms. If there is a large amount of cancer in the stomach, there may be blockages which prevent food from being digested properly. A blocked stomach can also cause stomach pain, vomiting and a feeling of bloating and being full after eating. The aim in this type of surgery is to make the patient more comfortable, not to cure.
Any surgery involving the stomach involves a major operation and a long period for recovery. Patients will typically have to stay in hospital for about two weeks after the procedure. This will be followed by several weeks recovering at home.
Radiation therapy (radiotherapy)
Beams of energy, such as X-rays, are target at cancer cells - the aim is to destroy them. The patient lies on a table and a machine moves around directing energy beams into specific parts of the body.
Radiotherapy is not commonly used for the treatment of stomach cancer because of the risk of harming other organs close to the body. However, if the cancer is advanced, for example, and causing bleeding or pain, radiotherapy is an option.
Neoadjuvant radiation - this refers to the use of radiation therapy before surgery to make the tumors smaller so that they can be removed more easily.
Adjuvant radiation - radiation therapy used after surgery. The aim is to kill off any remaining cancer cells around the stomach.
Radiation therapy is commonly used alongside chemotherapy. It may also be used to relieve the symptoms and side effects caused by large tumors in advanced cancer.
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 that have metastasized.
Neoadjuvant chemotherapy - administered before surgery. The aim being to make a tumor small so that it can be surgically removed more easily.
Adjuvant chemotherapy - administered after surgery to destroy any cancerous cells that may have remained behind.
Chemotherapy may also be administered in patients with advanced cancer to relieve the signs and symptoms of the disease.
Some patients may only receive chemotherapy (no surgery or radiation therapy), examples include some with gastrointestinal stromal tumors or gastric lymphoma.
Patients may experience side effects as a consequence of chemotherapy. The type of side effects depends on which chemotherapy medications are administered.
Examples include Sutent (sunitinib) and Gleevec (imatinib). They attack specific abnormalities with 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. Put simply, the benefits and risks are not well defined.