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Stomach Cancer

Posted by on Thursday, March 10, 2011, 3:11
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Although the incidence of stomach cancer has declined dramatically in the United States and Western Europe in the last 60 years, the disease remains a serious problem in much of the rest of the world, where it’s a leading cause of cancer death.

This global variation is almost certainly linked to two factors that play a major role in the development of stomach cancer — infection with Helicobacter pylori (H. pylori) bacteria and diet, especially the type of diet that’s high in salted, smoked and pickled foods common in areas that lack refrigeration as a means of preserving food.

Stomach Cancer
Stomach Cancer

Stomach cancer is more readily treated when caught early. Unfortunately, by the time stomach cancer causes symptoms, it’s often at an advanced stage and may have spread beyond the stomach. Yet there is encouraging news. You can reduce your risk of stomach cancer by making a few changes in your lifestyle.

Signs and Symptoms

One early sign of stomach cancer is microscopic internal bleeding, which is usually only detected by tests that check your stool for blood. You may also feel tired if this bleeding causes the loss of too many healthy red blood cells (anaemia). Early stomach cancer may also cause symptoms such as heartburn and abdominal pain, which can be mistaken for other, more common problems.

When the cancer is more advanced, you may experience signs and symptoms such as:

Discomfort in the upper or middle region of your abdomen that may not be relieved by food or antacids (In the early stages of stomach cancer, pain is often relieved by food or acid-buffering medications.)

Abdominal discomfort aggravated by eating
Black, tarry stools
Vomiting blood
Vomiting after meals
Weakness and fatigue
Unintended weight loss
Full feeling after meals, even when eating less than normal

Having one or more of these signs and symptoms doesn’t necessarily mean you have stomach cancer. Other more common conditions, especially peptic ulcers, can cause similar problems.

Causes

Your stomach is a muscular sac located in the upper middle of your abdomen, just below your ribs. The stomach walls are lined with three layers of powerful muscles that mix food with enzymes and acids produced by glands in the stomach’s inner lining. Your stomach’s delicate tissues are protected from this acidic mix by a thick, jelly-like mucus that coats the stomach lining.

Types of stomach cancer

o Adenocarcinomas. The great majority of stomach cancers are adenocarcinomas, which start in the glandular cells in the stomach’s innermost lining. Adenocarcinomas account for about 95 percent of all stomach cancers.

o Lymphomas. These are cancers of immune system tissue in the stomach wall. Some lymphomas are aggressive, whereas others grow much more slowly. The latter, known medically as mucosa-associated lymphoid tissue (MALT) lymphomas, usually stem from H. pylori infection and are often curable when found in the early stages.

o Carcinoid tumors. A small percentage of stomach cancers are carcinoid tumors that originate in the stomach’s hormone-producing cells. Carcinoid tumors tend to grow less quickly and spread (metastasize) less frequently than do the more common stomach cancers.

o Gastrointestinal stromal tumors (GISTs). Doctors believe that these rare tumors develop from cells called interstitial cells of Cajal, which are part of your autonomic nervous system. Your autonomic nervous system consists of the nerves that regulate the part of your nervous system that you can’t control, such as your heart rate, blood pressure and intestinal function.

Although GISTs can occur anywhere from the esophagus to the rectum, most are found in the stomach. Yet GISTs are not the same as other gastric cancers, differing not only in the cells in which they originate but also in their prognosis and treatment. A majority of GISTs have a specific genetic mutation that allows for treatment with a new form of cancer-specific therapy.

Why stomach cancer develops

Healthy cells grow and divide in an orderly way. This process is controlled by DNA — the genetic material that contains the instructions for every chemical process in your body. Some of the genes in your DNA promote cell division and some slow cell division or program cells to die at the right time. Still other genes control processes that help repair DNA. When DNA is damaged, these genes may not function properly, causing cells to grow out of control and eventually form a tumor — a mass of malignant cells.

Although the causes of many types of cancer aren’t clear, researchers have made progress in pinpointing factors that damage DNA in stomach cells and in understanding how that damage leads to cancer. These factors include:

o H. pylori infection. A majority of the world’s population is infected with corkscrew-shaped bacteria called Helicobacter pylori (H. pylori) that live deep in the mucous layer that coats the lining of the stomach. Although it’s not entirely clear how the bacteria are transmitted, it’s likely they spread from person to person through the oral-fecal route or are ingested in contaminated drinking water. H. pylori infection frequently occurs in childhood and can last throughout life if not treated. It’s the primary cause of stomach ulcers.

Having ulcers doesn’t necessarily put you at higher risk of stomach cancer, but having H. pylori infection does. That’s because long-term infection causes inflammation that can lead to precancerous changes in the stomach lining. One of these changes is atrophic gastritis, a condition in which the acid-producing glands are slowly destroyed. It’s likely that low acid levels prevent cancer-causing toxins from being properly broken down or flushed out of your stomach.

o Nitrates and nitrites. These are nitrogen-based chemicals that are added to certain foods, especially cured meats such as ham and bacon, hot dogs and deli meats. Both nitrates and nitrites combine with other nitrogen-containing substances in your stomach to form N-nitroso compounds — carcinogens that are known to cause stomach cancer.

o Salted, smoked or pickled foods and red meat. Before the advent of refrigeration, people commonly preserved food by salting, smoking or pickling. But these foods often contain large amounts of nitrites and nitrates, which can be converted in your stomach into cancer-causing compounds. Countries where consumption of salted meat and fish and pickled vegetables is high — Japan and Korea are notable examples — tend to have correspondingly high rates of stomach cancer. Eating a diet high in red meat, especially when the meat is barbecued or well-done, also has been linked to stomach cancer.

o Tobacco and alcohol use. Tobacco use can irritate the stomach lining, which may help explain why smokers have twice the rate of stomach cancer that non-smokers do. Alcohol has been associated with an increased risk of stomach cancer, but the link between the two isn’t clear.

Prevention

Although it may not be possible to prevent stomach cancer, the following steps can help reduce your risk:

o Emphasize fruits and vegetables. A diet rich in fresh fruits and vegetables, especially those high in vitamin C and beta carotene, has been shown to help protect against stomach cancer. Look for deep green and dark yellow or orange fruits and vegetables, such as Swiss chard, bok choy, spinach, cantaloupe, mango, acorn or butternut squash, and sweet potatoes. Also try to eat vegetables from the cabbage family, including broccoli, brussels sprouts and cauliflower. Lycopene, a nutrient found in tomatoes and other red fruits and vegetables such as strawberries and red bell peppers, may be a particularly powerful anti-cancer chemical.

o Avoid nitrites and nitrates. These nitrogen compounds are known to contribute to stomach cancer. They’re found primarily in processed meats — bologna, salami and corned beef, for instance — and in cured meats such as ham and bacon.

o Limit smoked, pickled and heavily salted foods. These have been linked to an increased risk of stomach cancer. Countries where the consumption of smoked, pickled and salted food is high have correspondingly high stomach cancer rates.

o Don’t smoke. Tobacco use greatly increases your risk of stomach cancer, especially cancer that occurs at the junction of the oesophagus and stomach.

o Limit alcohol consumption. Alcohol may cause changes in cells that can lead to cancer.

o Limit red meat. Eating large amounts of red meat — particularly when it’s barbecued or well-done — increases your risk of stomach cancer. Instead, choose fish or poultry.

o See your doctor if you have symptoms of an ulcer. Infection with H. pylori, the bacterium that causes most cases of gastric ulcers, is one of the leading causes of stomach cancer. Don’t ignore symptoms of ulcers, such as a gnawing pain in your abdomen or chest that’s worse when your stomach is empty or at night. Other, more severe signs and symptoms of ulcers include nausea, vomiting, bleeding and unintended weight loss.

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