An Overview of Stomach (Gastric) Cancer
The stomach is a sac-like organ connected to the esophagus on one end and the small intestine on the other. The stomach's main function is to store food and begin the digestive process. The stomach is not responsible for the absorption of nutrients—that process takes place in the intestines.
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The stomach can be divided into five parts:
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cardia or proximal stomach: the upper portion of the stomach closest to the esophagus; cells here produce acid and pepsin, which are used in the digestive process
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fundus: the section next to the cardia; cells here also produce acid and pepsin for digestion
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body: the main part of the stomach where food is stored
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antrum: where the digestive enzymes and the food are mixed together
- pylorus: the last part of the stomach that serves as a valve, controlling the amount of food and digestive enzymes that enter the small intestine.
The stomach is composed of four layers:
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mucosa: the innermost layer where stomach acid and digestive juices are made
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submucosa: a supporting layer
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muscularis: a layer of muscle that mixes the food with the digestive enzymes and moves the food through the stomach
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subserosa: a wrapping layer of the stomach
- serosa: the outermost wrapping layer of the stomach.
Stomach cancer, also known as gastric cancer, usually starts growing in the inner lining of the stomach. Cancer of the stomach usually takes years to develop, and early stages of the cancer usually show no symptoms. By the time symptoms become evident the prognosis is not good.
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Key Statistics about Gastric Cancer
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Each year, about 24,000 people in the US are diagnosed with gastric cancer.
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Each year, about 12,000 people in the US die from gastric cancer.
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The risk of developing stomach cancer in one's lifetime is about one in 100.
- Stomach cancer is the second leading cause of cancer death in the world with approximately 700,000 deaths each year.
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Causes and Risk Factors of Stomach Cancer
The exact cause of stomach cancer is unknown, but certain risk factors are known to increase the chance of stomach cancer. Some of the risk factors associated with stomach cancer include:
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Helicobacter pyloriinfection: The bacterium Helicobacter pylori (H. pylori) is believed to be a major risk factor for stomach cancer. Long-term infection of the stomach lining (atrophic gastritis) due to H. pylori may result in a change in the stomach lining that eventually develops into cancer.
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diet: A heavy diet of smoked, salted or pickled foods has been known to increase the risk of stomach cancer. This is a due to their high levels of nitrates and nitrites, which can be converted into cancer-causing compounds by naturally occurring bacteria in the stomach.
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alcohol and tobacco use: Alcohol and tobacco have been known to irritate the stomach lining. This irritation may eventually lead to cancer.
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obesity: Obesity greatly increases the risk of cancer of the stomach, especially the cardia.
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gender: Stomach cancer is twice as common in men than in women.
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ethnicity: Stomach cancer is most common in Asian/Pacific Islanders.
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age: The risk of stomach cancer greatly increases after the age of fifty.
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stomach polyps: Stomach polyps are often benign growths on the stomach lining, although some polyps can develop into cancer.
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blood type: People with type A blood tend to be at higher risk of developing stomach cancer.
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geography: People in certain areas of the world tend to be more likely to develop stomach cancer. This may be due to a multitude of factors, such as the local diet, for example.
- family history: People with relatives who have developed stomach cancer are at higher risk of developing stomach cancer themselves.
Symptoms of Gastric Cancer
Like many other cancers, early stage stomach cancers tend not to be asymptomatic—that is, no symptoms are apparent. This makes early detection very difficult, especially since many symptoms of stomach cancer can easily be mistaken for other, less serious stomach conditions. Some symptoms to look out for are:
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weight loss or loss of appetite
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discomfort or pain in the stomach/abdomen
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nausea
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fatigue
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vomiting
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a bloated feeling, especially after eating
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blood in the stool.
Stages and Prognosis of Stomach Cancer
Stomach cancer is staged using the TNM system, created by the American Joint Commission on Cancer (AJCC). The TNM system uses three pieces of information to determine he stage of cancer:
- size of the tumor and how far it has spread in the stomach (Tis-T4)
- extent of lymph node involvement (N0-N3)
- whether metastasis has occurred (M0-M1).
If stomach cancer is detected early, the disease is treatable and the prognosis is fairly positive. Unfortunately, most stomach cancers are diagnosed in the later stages, when the disease has already spread. By then, the cancer has advanced to the point where the prognosis is not very promising. Below is a chart of the stages, sub-stages, and their relative five-year survival rates.
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Stage |
TNM Stage |
Stage Description |
Five-Year Relative Survival Rate |
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0 |
Tis, N0, M0 |
The cancer is limited to the inner lining of the stomach (epithelium). |
89% |
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IA |
T1, N0, M0 |
The cancer has grown into the submucosa, the next layer. |
78% |
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IB |
T1, N1, M0
T2a/b, N0, M0 |
The cancer has either grown into the muscle layer and has spread to nearby lymph nodes (up to 6 lymph nodes), or has grown past the muscle layer, but has not spread to any lymph nodes. |
58% |
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II |
T1, N2, M0
T2a/b, N1, M0
T3, N0, M0 |
- The cancer has grown into the submucosa and has spread to 7-15 lymph nodes.
- The cancer has grown into the muscularis and possibly the subserosa and has spread to 1-6 lymph nodes.
- The cancer has grown into all 5 layers of the stomach but has not spread.
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34% |
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IIIA |
T2a/b, N2, M0
T3, N1, M0
T4, N0, M0 |
- The cancer has grown into the muscle layer and possibly beyond and has also spread to 7-15 lymph nodes.
- The cancer has grown into all 5 layers of the stomach and has spread to 1-6 lymph nodes.
- The cancer has grown into all 5 layers of the stomach as well as nearby organs.
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20% |
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IIIB |
T3, N2, M0 |
The cancer has grown beyond the muscle layer and has spread to 7-15 lymph nodes. |
8% |
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IV |
T4, N1-3, M0
T1-3, N3, M0
any T, any N, M1 |
- The cancer has grown into all five layers of the stomach and nearby organs.
- The cancer has spread to more than 15 lymph nodes.
- The cancer has metastasized.
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7% |
(Information obtained from the American Cancer Society)
Treatments for Stomach Cancer
The treatments for stomach cancer vary. The chosen treatment is dependent on the location of the cancer, the stage of the cancer, the patient's overall health and the choices made by the doctor and patient.
Stomach cancer treatments aim to completely eradicate the cancer. If that is not possible, the goal is to prevent the tumor from growing or to prevent the cancer from spreading any further. Treatment options also aim to relieve any symptoms one may be experiencing as a result of stomach cancer.
Some of the treatment options available to people with gastric cancer include:
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surgery: Surgery is the most common method of treatment for stomach cancer. The surgeon tries to remove the entire tumor, and while doing so, normally removes part or all of the stomach as well (gastrectomy). Local lymph nodes are also removed to prevent the cancer from spreading.
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chemotherapy: Chemotherapy uses systemic drugs injected into the bloodstream to kill cancer cells. Chemotherapy is often combined with another treatment option such as radiation therapy to improve the effectiveness of the treatment. One of the drawbacks of chemotherapy is the fact that it is a systemic treatment, and so may affect normal healthy cells as well as cancerous cells.
- radiation therapy: Radiation therapy employs a high-energy beam of radiation to kill cancer cells. This is a much more localized method of treatment than chemotherapy. A drawback of this method is that it may also destroy or alter healthy cells in the vicinity of the cancer.
Preventing Stomach Cancer
The cause of stomach cancer is unknown, but you can take certain precautions or change certain habits to lower the risk of stomach cancer. Some of these precautions or changes include:
- eating lots of fresh fruits and vegetables
- avoiding an excess of pickled, salted or smoked foods
- limiting intake of red meat
- exercising regularly
- quitting smoking
- avoiding the excessive consumption of alcohol.
Resources
American Academy of Family Physicians. (updated 2004). Stomach cancer.
American Cancer Society. (updated 2005). Detailed guide: Stomach cancer.
Mayo Foundation for Medical Education and Research. (updated 2005). Stomach cancer.
National Cancer Institute. (updated 2002). What you need to know about stomach cancer [NIH Publication No. 94-1554].
