Gastric Cancer

 The stomach is the primary organ of digestion. Food passes through the esophagus into the stomach at the level of the diaphragm, which is the breathing muscle that separates the abdomen from the chest. The stomach extends from the diaphragm to the duodenum, which is the first portion of the small intestine.

Cancer of the stomach is called gastric cancer. Gastric adenocarcinoma is the most common cancer of the stomach and it arises from the cells (columnar epithelium) lining the surface of the stomach. The primary risk factor associated with gastric cancer is infection with the bacteria, Helicobacter Pylori (H. pylori). In fact, 85% to 95% of all gastric cancers are believed to be caused by this infection. H. pylori is easily eradicated with antibiotics, which may prevent the development of this cancer.

There has been a marked decline in the incidence of gastric cancer in the United States and many other industrialized nations over the past 20-30 years. However, there has been an increase in cancers arising at the junction of the esophagus with the stomach. Approximately 22,600 new cases of gastric cancer are diagnosed in the United States each year, with approximately 13,700 yearly deaths from gastric cancer. Gastric cancer ranks 14th in incidence and is the 9th leading cause of cancer death in the US.

Gastric cancer is more common and is the major cause of cancer-related death in Asian countries such as Korea, China, Taiwan and Japan. Thus, much of the knowledge about treatment, especially surgery, comes from these countries. The incidence of gastric cancer is so high in these countries that they perform routine screening by esophagoscopy for detection of early gastric cancer. Early detection programs, such as those implemented in Japan, are not practiced elsewhere in the world because of the lower incidence of gastric cancer. For this reason, gastric cancer is detected at a later stage (extent of spread) in the U.S. and Europe than in Japan.

Surgery is the primary treatment of gastric cancer. Two main factors affect outcome following surgery for gastric cancer, the depth of the penetration of the primary cancer into the wall of the stomach and the presence or absence of spread of cancer to regional or adjacent lymph nodes. The site of the primary cancer also influences outcome, as upper stomach cancers are associated with a worse outcome than cancers of the middle and lower stomach.

Staging of Gastric Cancer
If possible, it is important to determine how much the cancer has spread before initiating treatment in order to select the best treatment option. Of particular concern is the presence of cancer in lymph nodes, spread of cancer to distant sites or local extension of cancer into surrounding structures, all of which might make attempts to remove all of the cancer with surgery impossible. Unfortunately, in many cases the true extent of spread of gastric cancer can only be determined at the time of surgical resection. Frequently, more advanced cancer is found during surgery than was detected through diagnostic procedures.

Routine Staging
All patients with gastric cancer undergo a routine chest x-ray examination and a barium swallow performed under fluoroscopy (direct x-ray examination). All patients have computerized tomography (CT) scans of the chest, upper abdomen and possibly the neck. There can be considerable error in CT scanning in detecting the extent of local spread of gastric cancer, but accuracy for detecting distant spread (metastasis) is good.

Gastroscopy: A gastroscopy is an examination performed through an endoscope, which is a flexible tube inserted through the esophagus that allows the physician to visualize, photograph and biopsy (sample) the cancer. All patients have a gastroscopy with a biopsy to determine the histology or appearance of the cancer under the microscope.

Endosonography: Endosonography refers to an ultrasound test performed through an endoscope. Ultrasound tests utilize sound waves to detect different densities of tissue, including cancer. Endosonography can detect spread of cancer into various layers of the stomach, adjacent organs and lymph nodes better than CT scanning.

Laparoscopy: Laparoscopy is a procedure that involves the insertion of an endoscope through a small incision in the abdomen. Laparoscopy is an important tool for staging and has proven to be more reliable than CT scanning in detecting spread of cancer to the liver and the lining of the abdomen (peritoneum). Ultrasonography can be performed through the laparoscope, thereby improving the accuracy of diagnosis. Another procedure, called peritoneal lavage, involves the infusion of fluid into the abdomen. Peritoneal lavage can increase the accuracy of diagnosis of peritoneal spread. Typically, patients who have cancer cells in the fluid from peritoneal lavage have a worse outcome.

Positron Emission Tomography (PET): Positron emission tomography (PET) scanning has also been used to improve the detection of cancer in lymph nodes. One characteristic of living tissue is the metabolism of sugar. Prior to a PET scan, a substance containing a type of sugar attached to a radioactive isotope (a molecule that spontaneously emits radiation) is injected into the patient’s vein. The cancer cells “take up” the sugar and attached isotope, which emits positively charged, low energy radiation (positrons). The positrons react with electrons in the cancer cells, which creates the production of gamma rays. The gamma rays are then detected by the PET machine, which transforms the information into a picture. If no gamma rays are detected in the scanned area, it is unlikely that the mass in question contains living cancer cells. In one clinical study, PET scanning detected 85% of lymph nodes involved with spread of gastric cancer, which was significantly better than the detection rate with CT scanning.

The current methods of clinical staging of patients with gastric cancer are not perfect and are constantly changing as new and more reliable tests are developed. At this point, the results of surgery are much more reliable in determining the extent of cancer spread than tests performed before surgery. In order to learn more about the most recent information available concerning the treatment of gastric cancer, click on the appropriate stage.

Stage 0: Cancer in situ is cancer that is limited to the surface layer of cells lining the stomach, which is called the epithelium.

Stage IA: Cancer invades beneath the surface layer of cells, but not into the muscle wall and there is no lymph node or distant spread of cancer.

Stage IB: Cancer invades beneath the surface layer of cells, with spread to 1-6 lymph nodes or invades into the muscle of the wall of the stomach without regional lymph node or distant spread of cancer.

Stage II: Cancer invades beneath the surface, with spread to 7-15 lymph nodes or invades into the muscle of the wall of the stomach, with 1-6 lymph nodes involved with cancer or cancer penetrates the outer wall of the stomach without invading local structures and without lymph node spread.

Stage III: Cancer has spread to adjacent structures and/or regional lymph nodes.

Stage IIIA: Cancer invades into the muscle of the wall of the stomach, with 7-15 lymph nodes involved or cancer invades the lining of abdomen (peritoneum) without invading local structures, with 1-6 lymph nodes involved or cancer invades the local structures without lymph node involvement.

Stage IIIB: Cancer invades the lining of the abdomen (peritoneum), with 7-15 lymph nodes involved.

Stage IV: Cancer invades adjacent structures, with 1-6 lymph nodes involved or any degree of invasion of the primary cancer with involvement of more than 15 lymph nodes or cancer is spread to local structures, with more than 7 lymph nodes involved or cancer has spread to distant sites.

Locally Advanced: Often, stages IB-IVA can also be referred to as locally advanced cancers.

Recurrent Cancer: The cancer has returned after primary treatment.

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