Stomach cancer

Definition

Stomach cancer (also known as gastric cancer) is a disease in which the cells forming the inner lining of the stomach become abnormal and start to divide uncontrollably, forming a mass called a tumor.

Description

The stomach is a J-shaped organ that lies in the left and central portion of the abdomen. The stomach produces many digestive juices and acids that mix with the food and aid in the process of digestion. There are five regions of the stomach that doctors refer to when determining the origin of stomach cancer. These are:

• the cardia, area surrounding the cardiac sphincter which controls movement of food from the esophagus into the stomach
• the fundus, upper expanded area adjacent to the cardiac region
• the antrum, lower region of the stomach where it begins to narrow
• the prepyloric, region just before or nearest the pylorus
• the pylorus, the terminal region where the stomach joins the small intestine.

Cancer can develop in any of the five sections of the stomach. Symptoms and outcomes of the disease will vary depending on the location of the cancer.

Demographics

In 2007, the American Cancer Society estimated that 21,260 Americans would be diagnosed with stomach cancer and approximately 11,210 deaths would result from the disease. The risk for developing stomach cancer in the United States is about 1 in 100. The risk is higher for men than for women. Two-thirds of stomach cancer cases are diagnosed in people older than age 65, but in families with a hereditary risk for stomach cancer, cases in younger individuals are more frequently seen.

Stomach cancer is one of the leading causes of cancer deaths in several areas of the world, most notably Japan and other Asian countries. In Japan it appears almost ten times as frequently as in the United States. The number of new stomach cancer cases is decreasing in some areas, however, especially in developed countries. In the United States, incidence rates of stomach cancer have declined. The use of refrigerated foods and increased consumption of fresh fruits and vegetables, instead of preserved foods with high salt content, may be a reason for the decline. Another reason for the decrease may be that antibiotics , which are given to treat childhood illnesses, can kill the bacterium Helicobacter pylori, which is a major cause of stomach cancer.

Causes and symptoms

While the exact cause for stomach cancer has not been identified, several potential factors have led to increased numbers of individuals developing the disease and, therefore, significant risk has been associated. Diet , work environment, exposure to the bacterium Helicobacter pylori, and a history of stomach disorders such as ulcers or polyps are some of these believed causes.

Studies have shown that eating foods with high quantities of salt and nitrites increases the risk of stomach cancer. The diet in a specific region can have a great impact on its residents. Making changes to the types of foods consumed has been shown to decrease likelihood of disease, even for individuals from countries with higher risk. For example, Japanese people who move to the United States or Europe and change the types of foods they eat have a far lower chance of developing the disease than do Japanese people who remain in Japan and do not change their dietary habits. Eating recommended amounts of fruit and vegetables may lower a person's chances of developing this cancer.

A high risk for developing stomach cancers has been linked to certain industries as well. The best proven association is between stomach cancer and persons who work in coal mining and those who work processing timber, nickel, and rubber. An unusually large number of these workers have been diagnosed with this form of cancer.

Several studies have identified a bacterium (Helicobacter pylori) that causes stomach ulcers (inflammation in the inner lining of the stomach). Chronic (long-term) infection of the stomach with these bacteria may lead to a particular type of cancer (lymphomas or mucosa-associated lymphoid tissue [MALT]) in the stomach.

Another risk factor is the development of polyps, benign growths in the lining of the stomach. Although polyps are not cancerous, some may have the potential to turn cancerous. People in blood group A are also at elevated risk for this cancer for unknown reasons. Other speculative causes of stomach cancer include previous stomach surgery for ulcers or other conditions, or a form of anemia known as pernicious anemia.

A history of smoking also increases the risk for developing stomach cancer. Smoking doubles the risk for the development of stomach cancer.

Stomach cancer is a slow-growing cancer. It may be years before the tumor grows very large and produces distinct symptoms. In the early stages of the disease, the patient may only have mild discomfort, indigestion, heartburn , a bloated feeling after eating, and mild nausea. In the advanced stages, a patient has loss of appetite and resultant weight loss , stomach pains, vomiting, difficulty in swallowing, and blood in the stool. Stomach cancer often spreads (metastasizes) to adjoining organs such as the esophagus, adjacent lymph nodes, liver, or colon.

Diagnosis

Unfortunately, many patients diagnosed with stomach cancer experience pain for two or three years before informing a doctor of their symptoms. When a doctor suspects stomach cancer from the symptoms described by the patient, a complete medical history is taken to check for any risk factors. A thorough physical examination is conducted to assess all the symptoms. Laboratory tests may be ordered to check for blood in the stool (fecal occult blood test) and anemia (low red blood cell count), which often accompany gastric cancer.

In some countries, such as Japan, it is appropriate for patients to be given routine screening examinations for stomach cancer, as the risk of developing cancer in that society is very high. Such screening might be useful for all high-risk populations. Due to the low prevalence of stomach cancer in the United States, routine screening is usually not recommended unless a family history of the disease exists.

Whether as a screening test or because a doctor suspects a patient may have symptoms of stomach cancer, endoscopy or barium x rays are used in diagnosing stomach cancer. For a barium x ray of the upper gastrointestinal tract, the patient is given a chalky, white solution of barium sulfate to drink. This solution coats the esophagus, the stomach, and the small intestine. Air may be pumped into the stomach after the barium solution in order to get a clearer picture. Multiple x rays are then taken. The barium coating helps to identify any abnormalities in the lining of the stomach.

In another more frequently used test, known as upper gastrointestinal endoscopy, a thin, flexible, lighted tube (endoscope) is passed down the patient's throat and into the stomach. The doctor can view the lining of the esophagus and the stomach through the tube. Sometimes, a small ultrasound probe is attached at the end of the endoscope. This probe sends high frequency sound waves that bounce off the stomach wall. A computer creates an image of the stomach wall by translating the pattern of echoes generated by the reflected sound waves. This procedure is known as an endoscopic ultrasound, or EUS.

Endoscopy has several advantages because the physician is able to see any abnormalities directly. In addition, if any suspicious-looking patches are seen, biopsy forceps can be passed painlessly through the tube to collect some tissue for microscopic examination. This is known as a biopsy. Endoscopic ultrasound (EUS) is beneficial because it can provide valuable information on depth of tumor invasion.

After stomach cancer has been diagnosed and before treatment starts, another type of x-ray scan is taken. Computed tomography (CT) is an imaging procedure that produces a three-dimensional picture of organs or structures inside the body. CT scans are used to obtain additional information in regard to how large the tumor is and what parts of the stomach it borders; whether the cancer has spread to the lymph nodes; and whether it has spread to distant parts of the body (metastasized), such as the liver, lung, or bone. A CT scan of the chest, abdomen, and pelvis is taken. If the tumor has gone through the wall of the stomach and extends to the liver, pancreas, or spleen, the CT will often show it. Although a CT scan is an effective way of evaluating whether cancer has spread to some of the lymph nodes, it is less effective than EUS in evaluating whether the nodes closest to the stomach are free of cancer. However, CT scans, like barium x rays, have the advantage of being less invasive than upper endoscopy.

Laparoscopy is another procedure used to stage some patients with stomach cancer. This involves a medical device similar to an endoscope. A laparoscopy is a minimally invasive surgery technique with one or a few small incisions, which can be performed on an outpatient basis, followed by rapid recovery. Patients who may receive radiation therapy or chemotherapy before surgery may undergo a laparoscopic procedure to determine the precise stage of cancer. The patient with bone pain or with certain laboratory results should be given a bone scan .

Benign gastric neoplasms are tumors of the stomach that cause no major harm. One of the most common is called a submucosal leiomyoma. If a leiomyoma starts to bleed, surgery should be performed to remove it. However, many leiomyomas require no treatment. Diagnosis of stomach cancers should be conducted carefully so that if the tumor does not require treatment the patient is not subjected to a surgical operation.

Other tests that may be performed to diagnosis stomach cancer include magnetic resonance imaging scan (MRI), positron emission tomography (PET) scan, and chest x ray .

Clinical staging

More than 95% of stomach cancers are caused by adenocarcinomas, malignant cancers that originate in glandular tissues. The remaining 5% of stomach cancers include lymphomas and other types of cancers.

It is important that gastric lymphomas be accurately diagnosed because these cancers have a much better prognosis than stomach adenocarcinomas. Approximately half of the people with gastric lymphomas survive five years after diagnosis.

Treatment for gastric lymphoma involves surgery combined with chemotherapy and radiation therapy.

Staging of stomach cancer is based on how deep the growth has penetrated the stomach lining; to what extent (if any) it has invaded surrounding lymph nodes; and to what extent (if any) it has spread to distant parts of the body (metastasized). The more confined the cancer, the better the chance for a cure.

One important factor in the staging of adenocarcinoma of the stomach is whether the tumor has invaded the surrounding tissue and, if it has, how deep it has penetrated. If invasion is limited, prognosis is favorable. Diseased tissue that is more localized improves the outcome of surgical procedures performed to remove the diseased area of the stomach. This is called a resection of the stomach.

Stomach cancer is staged using the Tumor(T), Node(N), Metastasis(M), classification system. After stage 0, where the cancer has not grown beyond the layers of the tissue lining the stomach, the tumor is labeled stage I through IV. Stage 1 indicates less tumor involvement; stage IV indicates the tumor has spread outside of the stomach and has invaded other tissues or organs in the body.

Treatment

Because symptoms of stomach cancer are so mild, treatment often does not commence until the disease is well advanced. The three standard modes of treatment for stomach cancer are surgery, radiation therapy, and chemotherapy. While deciding on the patient's treatment plan, the doctor takes into account many factors. The location of the cancer and its stage are important considerations. In addition, the patient's age, general health status, and personal preferences are also taken into account.

Surgery

In the early stages of stomach cancer, surgery may be used to remove the cancer. Surgical removal of adenocarcinoma is the only treatment capable of eliminating the disease. Laparoscopy is often used before surgery to investigate whether the tumor can be removed surgically. If the cancer is widespread and cannot be removed with surgery, an attempt is made to remove blockage and control symptoms such as pain or bleeding. Depending on the location of the cancer, a portion of the stomach may be removed, a procedure called a partial gastrectomy. In a surgical procedure known as total gastrectomy, the entire stomach may be removed. However, doctors prefer to leave at least part of the stomach if possible. Patients who have been given a partial gastrectomy achieve a better quality of life than those having a total gastrectomy. Even when the entire stomach is removed, the patients quickly adjust to a different eating schedule, which involves eating small quantities of food more frequently. High protein foods are generally recommended.

Partial or total gastrectomy is often accompanied by other surgical procedures. Lymph nodes are frequently removed and nearby organs, or parts of these organs, may be removed if cancer has spread to them. Such organs may include the pancreas, colon, or spleen.

Preliminary studies suggest that patients who have tumors that cannot be removed by surgery at the start of therapy may become candidates for surgery later. Combinations of chemotherapy and radiation therapy are sometimes able to reduce disease for which surgery is not initially appropriate. Preliminary studies were being performed as of 2008 to determine if some of these patients can become candidates for surgical procedures after such therapies are applied.

Chemotherapy

Whether patients undergoing surgery for stomach cancer should receive chemotherapy is controversial. Chemotherapy involves administering anti-cancer drugs either intravenously (through a vein in the arm) or orally (in the form of pills). This method can either be used as the primary mode of treatment or after surgery to destroy any cancerous cells that may have migrated to distant sites. Most cancers of the gastrointestinal tract do not respond well to chemotherapy; however, adenocarcinoma of the stomach and advanced stages of cancer are exceptions.

Although chemotherapy using a single medicine is sometimes used, the best response rates are often achieved with combinations of medicines. Therefore, in addition to studies exploring the effectiveness of new medicines, as of 2008 there were many clinical trials in progress attempting to evaluate how to best combine existing forms of chemotherapy to bring the greatest degree of help to patients.

Radiation therapy

Radiation therapy is often used after surgery to destroy the cancer cells that may not have been completely removed during surgery. To treat stomach cancer, external beam radiation therapy is generally used. In this procedure, high-energy rays from a machine that is outside of the body are concentrated on the area of the tumor. In the advanced stages of stomach cancer, radiation therapy is used to ease the symptoms such as pain and bleeding. However, studies of radiation treatment for stomach cancer have shown that the way it has been used it has been ineffective for many patients.

As of 2008 researchers were actively assessing the role of chemotherapy and radiation therapy used before a surgical procedure is conducted. They were searching for ways to use both chemotherapy and radiation therapy so that they increase the length of survival of patients more effectively than existing methods were able to do.

Nutrition/dietetic concerns

Following gastrectomy or partial gastrectomy it is important for patients to carefully follow doctor's orders about what foods are eaten and when they should be eaten. In particular, patients may be asked to have small, frequent meals.

QUESTIONS TO ASK YOUR DOCTOR

• Has the cancer spread to the lymph nodes?
• Has the cancer spread to the lungs, liver, or spleen?
• (After endoscopy or barium x-rays and CT scan have been completed) Would I benefit from endoscopic ultrasound or laparoscopy?
• (If surgery is recommended) Do recent studies show that it might be a good idea to also use chemotherapy or radiation therapy?
• (If gastrectomy or partial gastrectomy was performed) How should I alter my diet and eating patterns?
• (Following surgery) What foods should I eat? Is there a registered dietitian I can speak with on a regular basis about what I should eat?

Prognosis

In 2007, the American Cancer Society reported approximately 24% of patients with stomach cancer live at least five years following diagnosis. Patients diagnosed with stomach cancer in its early stages had a far better prognosis than those for whom it is in the later stages. In the early stages, the tumor is small, lymph nodes are unaffected, and the cancer has not migrated to the lungs or the liver. Unfortunately, only about 20% of patients with stomach cancer are diagnosed before the cancer had spread to the lymph nodes or formed a distant metastasis .

It is important to remember that statistics on prognosis may be misleading. Therapies are being developed rapidly and five-year survival has not yet been measured with all of these. Also, the largest group of people diagnosed with stomach cancer are between 60 and 70 years of age, suggesting that some of these patients die not from cancer but from other age-related diseases. As a result, some patients with stomach cancer in 2008 may be expected to have longer survival than did patients, for example, in 1998.

Prevention

Avoiding many of the risk factors associated with stomach cancer may prevent its development. Excessive amounts of salted, smoked, and pickled foods should be avoided, as should foods high in nitrates. A diet that includes recommended amounts of fruits and vegetables is believed to lower the risk of several cancers, including stomach cancer. The American Cancer Society recommends eating at least five servings of fruits and vegetables daily and choosing six servings of food from other plant sources, such as grains, pasta, beans, cereals, and whole grain bread. Following a healthy diet and balancing caloric intake with recommended amounts of physical activity may reduce obesity , which may itself be a risk for developing stomach cancer.

KEY TERMS

Adenocarcinoma —Malignant cancers that originate in the tissues of glands or that form glandular structures.

Anemia —A condition in which iron levels in the blood are low.

Barium x ray (upper GI) —An x-ray test of the upper part of the gastrointestinal (GI) tract (including the esophagus, stomach, and a small portion of the small intestine) after the patient is given a white, chalky barium sulfate solution to drink. This substance coats the upper GI and the x rays reveal any abnormality in the lining of the stomach and the upper GI tract.

Biopsy —Removal of a tissue sample for examination under the microscope to check for cancer cells.

Chemotherapy —Treatment of cancer with synthetic drugs that destroy the tumor either by inhibiting the growth of the cancerous cells or by killing the cancer cells.

Endoscopic ultrasound (EUS) —A medical procedure in which sound waves are sent to the stomach wall by an ultrasound probe attached to the end of an endoscope. The pattern of echoes generated by the reflected sound waves are translated by a computer into an image of the stomach wall.

External radiation therapy —Radiation therapy that focuses high-energy rays from a machine on the area of the tumor.

Infiltrate —A tumor that moves into another organ of the body.

Polyp —An abnormal growth that develops on the inside of a hollow organ such as the colon, stomach, or nose.

Radiation therapy —Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Total gastrectomy —Surgical removal (excision) of the entire stomach.

Upper endoscopy —A medical procedure in which a thin, lighted, flexible tube (endoscope) is inserted down the patient's throat. Through this tube the doctor can view the lining of the esophagus, stomach, and the upper part of the small intestine.

Abstaining from tobacco and excessive amounts of alcohol reduces the risk for many cancers. In countries where stomach cancer is common, such as Japan, early detection is important for successful treatment.

Treatment for H. pylori infection, especially for those individuals with chronic infections, may reduce the risk for developing stomach cancer.

Caregiver concerns

Many patients experience feelings of depression , anxiety , and fatigue when dealing with the knowledge of and treatments associated with stomach cancer. Side effects such as nausea and vomiting may also be experienced during treatment. Understanding what to expect as a result of the various treatments and learning about alternative methods for reducing these symptoms may improve the effectiveness of treatments and provide a more positive outlook in regard to the one's situation. A doctor or other health professional should be consulted to develop strategies for managing any negative symptoms or feelings.

Resources

other

“Gastric Cancer Treatment.” National Cancer Institute (NCI) February 22, 2008 [cited April 9, 2008]. http://www.cancer.gov/cancertopics/pdq/treatment/gastric/HealthProfessional

“Overview: Stomach Cancer.” American Cancer Society (ACS) 2008 [cited April 9, 2008]. http://www.cancer.org/docroot/CRI/CRI_2_1x.asp?rnav=criov&dt=40

organizations

American Cancer Society, PO Box 22718, Oklahoma City, OK, 73123-1718, (800) ACS-2345, https://www.cancer.org/.

National Cancer Institute, 6116 Executive Blvd., Room 3036A, Bethesda, MD, 20892-8322, (800) 422-6237, http://www.cancer.gov/.

National Coalition for Cancer Survivorship, 1010 Wayne Avenue, 5th Floor, Suite 300, Silver Spring, MD, 20910, (888) 650-9127, http://www.canceradvocacy.org/.

Lata Cherath Ph.D.

Bob Kirsch

Melinda Oberleitner R.N., D.N.S.