Gastric Cancer

Gastric Cancer



Definition of Gastric Cancer :

Stomach cancer, or gastric cancer, refers to cancer arising from any part of the stomach. Located in the upper abdomen between the esophagus and small intestine, the stomach serves as a reservoir where food is stored and partially digested after it is eaten. When food enters the stomach from the esophagus, the stomach churns the food and releases digestive juices to process the food before it enters the small intestine.
Gastric cancer occurs when cells in the stomach become abnormal and multiply. The abnormal cells may spread over time to invade deeper into the stomach wall, or eventually spread to nearby tissues or organs. 

Cause of Gastric Cancer:

Most stomach cancer is caused by Helicobacter pylori infection. Dietary factors are not proven causes, but some foods, such as smoked foods, salted fish and meat, and pickled vegetables are associated with a higher risk. Nitrates and nitrites in cured meats can be converted by certain bacteria, including H. pylori, into compounds that have been found to cause stomach cancer in animals. On the other hand, the American Cancer Society recommends eating fresh fruits and vegetables that contain antioxidant vitamins, such as A and C, and says that they lower the risk of stomach cancer, and a Mediterranean diet is associated with lower rates of stomach cancer.

Smoking increases the risk of developing gastric cancer significantly, from 40% increased risk for current smokers to 82% increase for heavy smokers. Gastric cancers due to smoking mostly occur in the upper part of the stomach near the esophagus Some studies show increased risk with alcohol consumption as well.

Other factors associated with increased risk are autoimmune atrophic gastritis, intestinal metaplasia, and genetic factors.

H. pylori is the main risk factor in 65–80% of gastric cancers, but in only 2% of such infections. The mechanism by which H. pylori induces stomach cancer potentially involves chronic inflammation, or the action of H. pylori virulence factors such as CagA. Approximately ten percent of cases show a genetic component. Some studies indicate that bracken consumption and spores are correlated with incidence of stomach cancer, though causality has yet to be established.

Gastric cancer shows a male predominance in its incidence as up to three males are affected for every female. Estrogen may protect women against the development of this cancer form. A very small percentage of diffuse-type gastric cancers are thought to be genetic. Hereditary Diffuse Gastric Cancer (HDGC) has recently been identified and research is ongoing. However, genetic testing and treatment options are already available for families at risk.

The International Cancer Genome Consortium is leading efforts to map stomach cancer’s complete genome.

Signs and Symptoms of Gastric Cancer:

Stomach cancer is often either asymptomatic (producing no noticeable symptoms) or it may cause only nonspecific symptoms (symptoms which are not specific to just stomach cancer, but also to other related or unrelated disorders) in its early stages. By the time symptoms occur, the cancer has often reached an advanced stage (see below) and may have also metastasized (spread to other, perhaps distant, parts of the body), which is one of the main reasons for its relatively poor prognosis. Stomach cancer can cause the following signs and symptoms:

Stage 1 (Early)

  • Indigestion or a burning sensation (heartburn)
  • Loss of appetite, especially for meat
  • Abdominal discomfort or irritation

Stage 2 (Middle)

  • Weakness and fatigue
  • Bloating of the stomach, usually after meals

Stage 3 (Late)

  • Abdominal pain in the upper abdomen
  • Nausea and occasional vomiting
  • Diarrhea or constipation
  • Weight loss
  • Bleeding (vomiting blood or having blood in the stool) which will appear as black. This can lead to anemia.
  • Dysphagia; this feature suggests a tumor in the cardia or extension of the gastric tumor into the esophagus.

Note that these can be symptoms of other problems such as a stomach virus, gastric ulcer or tropical sprue.

Risk Factors for Gastric Cancer :

Some of the factors that may increase the risk for development of gastric cancer include:

  • age over 55
  • autoimmune atrophic gastritis
  • intestinal metaplasia
  • male gender
  • ethnicity
  • smoking
  • genetic factors
  • eating smoked, salted, or pickled vegetables
  • the bacterial infection Helicobacter pylori

H. pylori is a common, treatable infection which leads to stomach inflammation and may increase the risk of developing gastric cancer.

Prevention from Gastric Cancer :

To reduce your risk of gastric cancer:

  • Do not smoke.
  • Avoid alcohol consumption
  • Eat a healthy foods rich in fruits and vegetables that contain antioxidant vitamins, such as A and C, and says that they lower the risk of stomach cancer, and a Mediterranean diet is associated with lower rates of stomach cancer
  • Avoid salted, pickled, smoked foods
  • Take medicines to treat reflux disease (heartburn), if you have it.
  • Take antibiotics if you are diagnosed with H. pylori infection.

Treatment of Gastric Cancer :

Cancer of the stomach is difficult to cure unless it is found in an early stage (before it has begun to spread). Unfortunately, because early stomach cancer causes few symptoms, the disease is usually advanced when the diagnosis is made. Treatment for stomach cancer may include surgery, chemotherapy, and/or radiation therapy. New treatment approaches such as biological therapy and improved ways of using current methods are being studied in clinical trials.

Surgery 

Surgery is the most common treatment. The surgeon removes part or all of the stomach, as well as the surrounding lymph nodes, with the basic goal of removing all cancer and a margin of normal tissue. Depending on the extent of invasion and the location of the tumor, surgery may also include removal of part of the intestine or pancreas. Tumors in the lower part of the stomach may call for a Billroth I or Billroth II procedure.

Endoscopic mucosal resection (EMR) is a treatment for early gastric cancer (tumor only involves the mucosa) that has been pioneered in Japan, but is also available in the United States at some centers. In this procedure, the tumor, together with the inner lining of stomach (mucosa), is removed from the wall of the stomach using an electrical wire loop through the endoscope. The advantage is that it is a much smaller operation than removing the stomach. Endoscopic submucosal dissection (ESD) is a similar technique pioneered in Japan, used to resect a large area of mucosa in one piece. If the pathologic examination of the resected specimen shows incomplete resection or deep invasion by tumor, the patient would need a formal stomach resection.

Surgical interventions are currently curative in less than 40% of cases, and, in cases of metastasis, may only be palliative.

Chemotherapy 

The use of chemotherapy to treat stomach cancer has no firmly established standard of care. Unfortunately, stomach cancer has not been particularly sensitive to these drugs, and chemotherapy, if used, has usually served to palliatively reduce the size of the tumor, relieve symptoms of the disease and increase survival time. Some drugs used in stomach cancer treatment have included: 5-FU (fluorouracil) or its analog capecitabine, BCNU (carmustine), methyl-CCNU (Semustine), and doxorubicin (Adriamycin), as well as Mitomycin C, and more recently cisplatin and taxotere, often using drugs in various combinations. The relative benefits of these different drugs, alone and in combination, are unclear. Clinical researchers have explored the benefits of giving chemotherapy before surgery to shrink the tumor, or as adjuvant therapy after surgery to destroy remaining cancer cells. Combination treatment with chemotherapy and radiation therapy has some activity in selected post surgical settings. For patients who have HER2 overexpressing metastatic gastric or gastroesophageal (GE) junction adenocarcinoma, who have not received prior treatment for their metastatic disease, the US Food and Drug Administration granted approval (2010 October) for trastuzumab (Herceptin, Genentech, Inc.) in combination with cisplatin and a fluoropyrimidine (capecitabine or 5-fluorouracil). This was based on an improvement of the median overall survival (OS) of 2.5 months with trastuzumab plus chemotherapy treatment compared to chemotherapy alone (BO18255 ToGA trial). The combination of Herceptin with chemotherapy for treating metastatic gastric cancer was also sanctioned by the European regulatory authorities (2010 January).

Radiation

Radiation therapy (also called radiotherapy) is the use of high-energy rays to damage cancer cells and stop them from growing. When used, it is generally in combination with surgery and chemotherapy, or used only with chemotherapy in cases where the individual is unable to undergo surgery. Radiation therapy may be used to relieve pain or blockage by shrinking the tumor forpalliation of incurable disease.

Multimodality therapy

While previous studies of multimodality therapy (combinations of surgery, chemotherapy and radiation therapy) gave mixed results, the Intergroup 0116 (SWOG 9008) study showed a survival benefit to the combination of chemotherapy and radiation therapy in patients with nonmetastatic, completely resected gastric cancer. Patients were randomized after surgery to the standard group of observation alone, or the study arm of combination chemotherapy and radiation therapy. Those in the study arm receiving chemotherapy and radiation therapy survived on average 36 months; compared to 27 months with observation.