A Helicobacter pylori infection is a risk factor for stomach cancer.
Vague abdominal discomfort, weight loss, and weakness are some typical symptoms.
Diagnosis includes endoscopy and biopsy.
The survival rate is low because the cancer tends to spread early to other sites.
Surgery is performed to eliminate the cancer or relieve symptoms.
About 95% of stomach cancers are adenocarcinomas. Adenocarcinomas of the stomach originate from the glandular cells of the stomach lining.
In the United States, stomach cancer occurs in about 26,240 people each year and causes almost 10,800 deaths per year. In the United States, it is more common among certain populations: people aged 50 and older, blacks, Hispanics, and American Indians. For unknown reasons, adenocarcinoma of the stomach is becoming less common in the United States. Worldwide, stomach cancer is the second most common cancer. It is far more common in Japan, China, Chile, and Iceland. In these nations, screening programs are an important means of early detection.
Lymphoma is cancer of the lymphatic system. Lymphoma can develop within the stomach. Helicobacter pylori infection, which is a cause of stomach ulcers, is believed to play a role in the development of some lymphomas of the stomach. People with stomach lymphoma who have active H. pylori infection are treated with antibiotics, and others are given radiation therapy. surgery and chemotherapy are used less often. Stomach lymphoma responds to treatment better than adenocarcinoma. Longer survival and even cure are possible.
Leiomyosarcoma (cancer of smooth muscle cells) can develop in the wall of the stomach. It is also called a spindle cell tumor. It is best treated with surgery. If cancer has already spread (metastasized) to other parts of the body at the time a leiomyosarcoma is found, then chemotherapy may lead to slightly longer survival. The drug imatinib has been found to be effective in treating leiomyosarcoma that cannot be treated with surgery.
Adenocarcinoma of the stomach often begins at a site where the stomach lining is inflamed. Helicobacter pylori infection is a risk factor for some stomach cancers. People who have certain gene mutations are also at risk as are people who have autoimmune atrophic gastritis.
Stomach polyps may become cancerous (malignant) and are thus removed. Adenocarcinoma of the stomach is particularly likely to develop if the polyps consist of glandular cells, if the polyps are larger than ¾ inch (2 centimeters), or if several polyps exist.
Certain dietary factors were once thought to play a role in the development of adenocarcinoma of the stomach. These factors included a high intake of salt, a high intake of carbohydrates, a high intake of preservatives called nitrates (often present in smoked foods), and a low intake of fruit and green leafy vegetables. Although none of these factors has proved to be a cause, a direct link between the consumption of processed meat and stomach cancer has been reported.
Smoking is a risk factor for stomach cancer. People who smoke may not respond as well to treatment.
In the early stages, symptoms of stomach cancer are vague and easily ignored. Early symptoms may mimic those of peptic ulcer disease, with burning abdominal pain. Therefore, peptic ulcer symptoms that do not resolve with treatment may indicate stomach cancer. The person may notice a feeling of fullness after a small meal (early satiety).
People may begin to feel full after eating sooner than they normally do. They may have weight loss or weakness caused by difficulty eating or by an inability to absorb some vitamins and minerals. Anemia, characterized by fatigue, weakness, and light-headedness, may result from very gradual bleeding that causes no other symptoms, from malabsorption of vitamin B12 (a vitamin needed for red blood cell formation), or from malabsorption of iron (a mineral needed for red blood cell formation) due to a lack of stomach acid. Uncommonly, a person may vomit large amounts of blood (hematemesis) or pass black tarry stools (melena). When adenocarcinoma is advanced, a doctor may be able to feel a mass when pressing on the abdomen.
Even in the early stages, a small adenocarcinoma may spread (metastasize) to distant sites. The spread of the tumor may cause liver enlargement, a yellowish discoloration of the skin and the whites of the eyes (jaundice), fluid accumulation and swelling in the abdominal cavity (ascites), and swollen lymph nodes. The spreading cancer also may weaken bones, leading to bone fractures.
Endoscopy (an examination in which a flexible tube is used to visualize the inside of the digestive tract) is the best diagnostic procedure. It allows a doctor to view the stomach directly, to check for Helicobacter pylori, and to remove tissue samples for examination under a microscope (biopsy). Barium x-rays are used less often because they rarely reveal small early-stage cancers and do not allow for biopsy.
If cancer is found, people usually have a CT scan of the chest and abdomen to determine the extent to which the tumor has spread to other organs. If the CT scan does not show the tumor has spread, doctors usually perform an endoscopic ultrasound (which shows the lining of the digestive tract more clearly because the probe is placed on the tip of the endoscope) to determine the depth of the tumor and the involvement of nearby lymph nodes.
Basic blood tests are done including complete blood count, electrolytes, liver blood tests, and carcinoembryonic antigen level.
Fewer than 5 to 15% of people with adenocarcinoma of the stomach survive longer than 5 years. The cancer tends to spread early to other sites.
The prognosis is good if the cancer has not penetrated the stomach wall too deeply. In such cases, up to 80% of people may survive for 5 years. However, in the United States, the results of surgery are often poor, because most people have extensive cancer by the time a diagnosis is made. In Japan, where stomach cancer is very common, mass public health screening programs help to detect it early so that a cure is more likely.
If the cancer has not spread beyond the stomach, surgery is usually done to try to cure it. Removal of the entire tumor before it has spread offers the only hope of cure. Most or all of the stomach and nearby lymph nodes are removed.
If the cancer has spread beyond the stomach, surgery cannot cure the condition, but it is sometimes used to relieve symptoms. For example, if the passage of food is obstructed at the far end of the stomach, a bypass operation, in which an alternate connection is made between the stomach and the small intestine, allows food to pass. This connection relieves the symptoms of obstruction—pain and vomiting—at least for a while.
Chemotherapy plus radiation therapy (see Combination Cancer Therapy) may help relieve symptoms as well but does little to help people survive longer than 5 years. In recent years, chemotherapy has been combined with trastuzumab and ramucirumab to treat people who have advanced cancer.
Immunotherapy, such as pembrolizumab, may be given to people who have stomach cancer that is advanced or has spread (metastasized) and is PD-L1–positive. This therapy enhances the immune system’s ability to fight cancer.
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