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Stomach Cancer

Definition :
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 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.

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

  • 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.
  • 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.
  • 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.
  • 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 :

  • 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.

  • 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.
  • 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.
  • 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 nonsmokers do. Alcohol has been associated with an increased risk of stomach cancer, but the link between the two isn't clear.

Risk Factor :
Having H. pylori infection makes you more likely to develop stomach cancer than someone who doesn't have the infection. Even so, most people with H. pylori don't get stomach cancer, and researchers believe that genetic factors make some people more susceptible to the disease.

Other risk factors for stomach cancer include :

  • Your sex. Men have double the rate of stomach cancer that women do.
  • Age. Most people who develop stomach cancer are older than 50 years.
  • Diet. A diet high in foods preserved by smoking, salting or pickling increases your risk of stomach cancer. So do foods that contain nitrites and nitrates, such as bacon, ham and processed meats. Eating large amounts of red meat — particularly if it's barbecued or well-done — also increases your risk. On the other hand, consuming plenty of fruits and vegetables, especially those that are red or deep yellow, such as tomatoes, carrots and sweet potatoes, helps protect against stomach cancer.
  • Tobacco use. Smokers have twice the incidence of stomach cancers that nonsmokers do.
  • Previous stomach surgery. The risk of stomach cancer may increase in people who have had part of their stomach and the opening to the small intestine (pyloric valve) removed — usually as a treatment for peptic ulcers. After stomach surgery, bile and sometimes pancreatic juices can back up, causing irritation and inflammation of the stomach lining (gastritis). In addition, the amount of protective stomach acid decreases while nitrite-producing bacteria may increase. These factors can lead to stomach cancer in some people. In general, the risk is greatest for the first 20 years after the initial surgery.
  • Stomach polyps. These are small growths in the lining of your stomach. Most are noncancerous (benign), but adenomatous polyps may be precancerous.
  • Familial cancer syndromes. These include hereditary nonpolyposis colon cancer and familial adenomatous polyposis, inherited disorders that slightly increase your risk of stomach cancer. People who carry mutations in the BRCA1 and BRCA2 genes also have an increased stomach cancer risk. These mutations were previously thought to be associated only with breast and ovarian cancers.
  • Family history. You're more likely to develop stomach cancer if you have a parent or sibling with the disease.
  • Pernicious anemia. This condition, which is often associated with atrophic gastritis, develops when your stomach is no longer able to make a protein called intrinsic factor that helps your body absorb vitamin B-12. Although pernicious anemia is easily treated with B-12 injections, having the disease can slightly increase your risk of stomach cancer.
  • Type A blood. Your blood type is determined by the presence or absence of two proteins — A and B — that occur on red blood cells. For reasons that aren't clear, people with type A blood have a somewhat higher risk of stomach cancer than do people with other blood types.
  • Country of origin. Stomach cancer is more common in some parts of the world — especially Japan, Korea, parts of Eastern Europe, and Latin America — than it is in the United States. These differences are likely related to diet and H. pylori infection. Stomach cancer occurs most often in countries where large amounts of meat or smoked, heavily salted or pickled foods are consumed, or where there is a lack of refrigeration as a means to preserve food.
  • Obesity. Extra weight has been associated with an increased risk of some cancers, including stomach cancer.

When to seek medical advice :
Stomach cancer is treatable if caught early. Unfortunately, it rarely causes symptoms in the beginning stages. When symptoms do occur, they're often vague and can easily be mistaken for other, more common but less serious problems such as a stomach virus or heartburn. Less than one in five stomach cancers are diagnosed before they have spread outside the stomach.

See your doctor if you have a persistent feeling of discomfort in the upper or middle region of your abdomen, especially if it occurs in conjunction with fatigue and weight loss.

And see your doctor right away if you develop black, tarry stools or if you vomit after meals. Although not always indicators of stomach cancer, these signs may result from other conditions that require medical care.

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 (anemia). 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.

Diagnosis :
To help diagnose stomach cancer and rule out other possibilities, your doctor may recommend one or more of the following diagnostic tests :

  • Upper endoscopy. This procedure allows your doctor to see abnormalities in your upper gastrointestinal (GI) tract that may not be visible on X-rays. For the test, your doctor inserts a thin, flexible, lighted tube (endoscope) through your mouth and into your esophagus, stomach and the first part of your small intestine. Your throat is usually numbed before you're asked to swallow the endoscope, and you'll usually receive intravenous medication to ensure that you're comfortable during the procedure.

    If any tissue in your upper intestinal tract looks suspicious, your doctor can remove a small sample (biopsy) using instruments inserted through the endoscope. The sample is then sent to a lab for examination by a pathologist.

    Upper endoscopy takes about 20 to 30 minutes, although you won't be sent home until the medication wears off — usually one to two hours later. Risks of the procedure are rare and include bleeding and perforation of the stomach lining. The most common complication is a slight sore throat from swallowing the endoscope.

  • Stomach X-ray (barium upper GI series). This test uses a series of X-rays to examine your esophagus, your stomach and the first part of your small intestine.

    Before the test, you'll drink a thick liquid (barium) that temporarily coats the lining of your stomach so that it shows up clearly on the X-rays. You may also be asked to swallow a gas-producing liquid or pill, such as sodium bicarbonate, which stretches the stomach and separates its folds, thereby providing a better view of the inner lining.

    After the test you can eat normally and resume your usual activities, although you'll need to drink extra water to help flush the barium from your system. The most common complication of the procedure is temporary constipation.

If you receive a diagnosis of stomach cancer, your doctor is likely to recommend additional tests to help determine the extent of the disease (staging tests) and the best course of treatment. These may include :

  • Endoscopic ultrasound. This test helps determine whether cancer has spread into the walls of your stomach or to nearby tissues and lymph nodes. Endoscopic ultrasound is similar to upper endoscopy, but in this case, the endoscope carries a small ultrasound probe that uses high-frequency sound waves to create images of your stomach and surrounding tissues, including lymph nodes.
  • Computerized tomography (CT) scan. Used to help check for the spread of cancer outside your stomach — especially to organs such as your liver and lungs — this test uses split-second computer processing and X-ray beams to produce detailed cross-sectional images of your internal organs. A CT scan exposes you to more radiation than conventional X-rays do, but in most cases, the benefits outweigh the risks.
  • Magnetic resonance imaging (MRI). This test also looks for the spread of cancer beyond your stomach. But unlike a CT scan, MRI uses a powerful magnetic field and radio waves — not X-rays — to produce cross-sectional images of your body.
  • Chest X-ray. This test checks whether cancer has spread to your lungs but isn't as sensitive as a CT scan.

Treatment:
The kind of treatment you receive for stomach cancer depends on a number of factors, including the location of the cancer, how advanced it is, your overall health and your own preferences. Especially when cancer is advanced, choosing a treatment plan is a major decision, and it's important to take time to evaluate your choices.

You may also want to consider seeking a second opinion. This can provide additional information to help you feel more certain about the option you're considering.

The goal of any treatment is always to eliminate the cancer completely. When that isn't possible, the focus may be on preventing the tumor from growing or causing more harm. In some cases, an approach called palliative care may be best. Palliative care refers to treatment aimed not at removing or slowing the disease, but at helping relieve symptoms and making you as comfortable as possible.

Stomach cancer treatment options include the following :

  • Surgery. This is the most common treatment for stomach cancer. Depending on the extent of the cancer, your doctor may remove part (subtotal, or partial, gastrectomy) or all (total gastrectomy) of your stomach as well as some of the surrounding tissue. Lymph nodes near the tumor also are often removed during surgery. After a subtotal gastrectomy, the remaining part of your stomach is connected to your esophagus and your small intestine. If your entire stomach is removed, your surgeon attaches your esophagus directly to your small intestine. A 2006 study suggested that chemotherapy before and after surgery may improve outcomes for certain people, so discuss this with your doctor.

    When stomach cancer is caught at an early stage and your surgeon is able to remove the entire tumor, a complete recovery is possible. Unfortunately, diagnosis usually doesn't occur until stomach cancer has spread through the stomach wall to nearby lymph nodes or other organs. At this point, it's not possible to remove all the cancer surgically, but your doctor may still recommend an operation to alleviate pain, bleeding or obstruction. In some cases of advanced stomach cancer, a laser beam directed through an endoscope can vaporize most of the tumor and relieve obstruction without an operation.

    After gastrectomy, some people experience leakage or obstruction where the intestinal tract has been reconstructed. More common problems associated with partial or total gastrectomy include diarrhea, vomiting and dumping syndrome, which occurs when the small intestine fills too quickly with undigested food. Signs and symptoms of dumping may occur immediately after eating (early dumping) or several hours after a meal (late dumping) and include nausea, vomiting, diarrhea, cramping and dizziness.

  • Chemotherapy. This treatment uses drugs to help kill cancer cells. Injected into a vein or taken orally, chemotherapy medications travel through your bloodstream and are often used to eliminate cancer cells that may remain after surgery or to treat cancers that have spread to other parts of the body. Chemotherapy may also be used to control cancer growth, prolong life or relieve symptoms of advanced disease. Although it sometimes may be the only treatment needed, doctors most often use chemotherapy in conjunction with other therapies. For example, in locally advanced stomach cancer, which occurs when the tumor affects only the stomach and nearby tissues, chemotherapy and radiation (radiotherapy) may be offered after surgery to help increase survival and improve quality of life.

    A 2006 study found that people whose stomach cancer hadn't spread had better outcomes when chemotherapy was used both before and after surgery to remove the cancer. In the study, people with stomach cancer were randomly assigned to receive surgery alone or to receive three cycles of chemotherapy before surgery and three cycles of chemotherapy after recovering from surgery. People in this study who received surgery combined with chemotherapy lived somewhat longer and had a lower risk of the cancer returning than did people who received surgery only.

    Because anti-cancer drugs affect healthy cells as well as cancerous ones — especially fast-growing cells in your digestive tract and bone marrow — side effects such as nausea and vomiting, fatigue, and an increased risk of infection due to a shortage of white blood cells are common. Although not everyone experiences these side effects, chemotherapy can sometimes feel like another illness and is often the part of treatment about which people are most apprehensive. But newer anti-nausea medications can prevent or reduce most nausea. Sometimes acupuncture or relaxation techniques, such as guided imagery, meditation and deep breathing, also may help control nausea and vomiting. Chemotherapy is normally administered in cycles, with periods of treatment alternating with periods of recovery during which your body can recover. Ask your treatment team about the side effects of any treatment you're considering and the best ways to minimize those effects.

  • Radiation therapy (radiotherapy). This therapy uses high-energy X-rays to kill cancer cells. Unlike chemotherapy, which affects your entire body, radiation affects only those parts of your body through which the radiation beam passes. Because any tissue touched by radiation can be damaged, doctors are careful to aim the beam in a way that's least likely to harm healthy tissue. Radiation that comes from a machine outside your body (external beam radiation) is generally used to treat stomach cancer, especially in conjunction with chemotherapy. It may also help relieve pain and blockages. Side effects may include a burn similar to sunburn on your skin where the radiation enters your body, nausea, vomiting, and fatigue that may increase over the course of treatment.
  • Antibiotics. Carefully selected individuals who have H. pylori-associated gastric lymphomas may be cured by antibiotic therapy that eliminates the bacteria causing this cancer. If you have this type of cancer, your doctor will need to carefully monitor your condition for recurrence or for the presence of more advanced disease that requires more aggressive therapy.

Targeted drug therapy
The Food and Drug Administration has approved the anti-leukemia drug imatinib mesylate (Gleevec) to treat gastrointestinal stromal tumors (GISTs) that contain a specific genetic mutation. Imatinib, which is taken in capsule form once a day, belongs to a class of medications that target a specific genetic mutation within cancer cells but leave healthy tissue relatively untouched. Side effects tend to be milder than with other types of cancer therapy and include fluid retention (edema), nausea, muscle cramps and rash.

Imatinib is effective only for GISTs that have a specific genetic mutation and even then, it isn't for everyone — surgical removal remains the primary therapy for this type of cancer. Despite promising results in some people, imatinib isn't effective in all cases nor are the long-term effects known.

Clinical trials
If you have advanced stomach cancer, you may want to consider participating in a clinical trial. This is a study that's used to test new forms of therapy — typically new drugs, different approaches to surgery or radiation treatments, and novel methods such as gene therapy. If the therapy being tested proves to be safer or more effective than current treatments, it will become the new standard of care.

The treatments used in clinical trials haven't yet proved effective. They may have serious or unexpected side effects, and there's no guarantee you'll benefit from them.

On the other hand, cancer clinical trials are closely monitored by the federal government to ensure they're conducted as safely as possible. And they offer access to treatments that wouldn't otherwise be available to you.

If you're interested in finding out more about clinical trials, talk to your treatment team. You can also call the National Cancer Institute's Cancer Information Service at 800-4-CANCER, or 800-422-6237. The call is free and trained specialists are available to answer your questions.

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

  • 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.
  • 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.
  • 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.
  • Don't smoke. Tobacco use greatly increases your risk of stomach cancer, especially cancer that occurs at the junction of the esophagus and stomach.
  • Limit alcohol consumption. Alcohol may cause changes in cells that can lead to cancer.
  • 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.
  • 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.
 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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