This mostly affects older people. The average age of people when they are diagnosed is 68. About six out of every ten persons diagnosed with stomach cancer each year are 65 or older. The risk that a man will develop stomach cancer in his lifetime is about 1:95. For women, the risk is about 1:154. In the United States, the number of new cases of stomach cancer has decreased by 1.5% each year over the last 10 years. Stomach cancer is much more common in other parts of the world, particularly in the less developed countries. It is however, one of the leading causes of cancer-related deaths in the world. The decreasing incidence of stomach cancer in the United States may be linked to the increased use of refrigeration for food storage, plus decrease the use of salted and smoked foods. It may also be linked to the frequent use of antibiotics to treat infections which may have killed the Helicobacter pylori bacteria which is thought to be the major cause of stomach cancer.
What Causes Stomach Cancer?
There are many known risk factors for stomach cancer but it is not known how these factors cause cells of the stomach lining to become cancerous. This is still the subject of numerous research.
Several changes which are thought to be precancerous occur in the stomach lining:
Chronic Atrophic Gastritis
In this condition, the normal glands of the stomach are either decreased or absent. There is also some degree of inflammation as the stomach cells are damaged by cells of the immune system. Atrophic gastritis is often caused by H. pylori infection. It can also be caused by an autoimmune reaction, in which a person’s immune system attacks the cells lining the stomach. Some people with this condition go on to develop pernicious anaemia or other stomach problems including cancer. It is not known how this condition progresses to cancer.
This is another possible precancerous change whereby the normal lining of the stomach is replaced with cells that closely resemble the cells that usually line the intestine. Patients with this condition usually have chronic atrophic gastritis as well. How and why this change occurs and progresses to stomach cancer is not well understood. This may be related to H. pylori infection.
Recent research has, however, provided clues on how some stomach cancers can form. For instance, H. pylori bacteria, particularly certain subtypes, can develop substances in some foods into chemicals that cause mutations in the DNA of the cells of the stomach lining. This may also explain why certain foods such as preserved meats increase a person’s risk for stomach cancer. On the other hand, some of the foods that might lower stomach cancer risk, such as fruits and vegetables, contain antioxidants that can block substances that damage the cell’s DNA.
Much progress and understanding now occurs in understanding how changes in DNA can cause normal stomach cells to grow abnormally and form cancer. Genes that help cells grow and divide are called oncogenes.
Genes that help keep cell division under control or cause cells to die at the right time are called tumour suppressor genes. DNA changes that turn oncogenes or turn off tumour suppressor genes can cause cancers. Inherited mutations in some genes can increase a person’s stomach cancer risk. However, these are thought to cause only a small percentage of stomach cancers. Still genetic testing can be done to look for gene mutations that can cause some inherited cancer syndromes. Most of the gene changes that lead to stomach cancer occur after birth. Some of these changes are caused by risk factors such as H. pylori infection or tobacco use, but other gene changes may just be random events that sometimes happen inside cells without having an outside cause.
Can Stomach Cancer be Found Early?
In countries such as Japan where stomach cancer is very common, mass screening of the population has helped find many cases at an early curable stage. This may have reduced the number of people who have died of this disease, but this is not proven. Unfortunately, studies have not found that routine screening in people with average risk for stomach cancer is useful because this disease is not that common.
On the other hand, patients with certain stomach cancer risk factors may benefit from screening. As a result of the fact that there is no routine screening, most people with this disease are not diagnosed until they have certain symptoms and signs that point to the need for further investigation.
Signs and Symptoms of Stomach Cancer
Early stage stomach cancer rarely causes symptoms. Signs and symptoms include:
- Poor appetite – weight loss
- Abdominal pain
- Vague discomfort
- A sense of fullness in the upper abdomen after eating a small meal
- Heartburn or indigestion
- Nausea, vomiting with or without blood
- Swelling or fluid build-up in the abdomen
- Blood in the stool
- Low red blood cell count
- Painful swallowing
- Vomiting blood.
Upper Gastrointestinal Endoscopy
If anyone has any of these symptoms, then they should be referred urgently for upper GI endoscopy. This is the main test to find stomach cancer.
Can Stomach Cancer be Prevented?
Diet, nutrition, bodyweight and physical activity.
Being overweight or obese increases the risk of some types of stomach cancer, so staying healthy and at a healthy weight might lower your risk.
Getting regular physical activity also might lower your risk.
A diet high in fresh fruits and vegetables may reduce the stomach cancer risk. Citrus fruits may also be helpful.
Alcohol probably increases the risk of stomach cancer so avoiding or limiting alcohol might lower your risk.
Studies which have reviewed dietary supplements have had mixed results. Some studies have suggested that a combination of antioxidant supplements, vitamin A, C and E and the mineral selenium might reduce the risk of stomach cancer in people with poor nutrition to begin with. Most studies looking at people who have had good nutrition have not found any benefit to adding vitamin pills to their diet. However, further research is required. Some small idiosyncratic studies have suggested that drinking tea, particularly green tea, may help to avoid stomach cancer. However, most large studies have not found this link.
Avoiding Tobacco Use
Tobacco use can increase the risk of cancers of the proximal stomach. It would be recommended to stop smoking.
Treating H. Pylori Infection
It is still unclear whether patients whose stomach linings are chronically infected with H. pylori bacteria should or should not be treated if they have no symptoms. This is currently a topic of research. Some early studies have suggested that giving antibiotics to people with H. pylori infection might lower the number of precancerous lesions in the stomach and reduce the risk of developing stomach cancer. However, not all studies have proven this. More research is required.
Using aspirin or other non-steroidal anti-inflammatories, such as Ibuprofen seem to lower the risk of stomach cancer. It is felt that if one is taking these medications for other reasons then the reduced cancer risk is an additional benefit, but it is not routinely recommended to take non-steroidal anti-inflammatories to prevent stomach cancer. There are serious complications with these drugs such as bleeding and studies have not as yet determined which patients benefit from this lowering cancer risk as opposed to the side effect risk of bleeding.
For Patients at a Grossly Increased Risk
Only a small percentage of stomach cancers are known to be caused by hereditary diffuse gastric cancer syndrome, but it is important to recognise this. Most patients who inherit this condition eventually get stomach cancer. A personal history of invasive lobular breast cancer before the age of 50 as well as having close family members who have had stomach cancer suggest that they might be at risk of having this syndrome. These patients should be referred to a clinical geneticist for genetic counselling. Another hereditary cancer with an increased risk of stomach cancer is Lynch syndrome.
To learn more about Health Screening at The London General Practice please visit our web site.