Stomach cancer risks and causes Useful information Contents This information is about possible risk factors and causes for stomach cancer. Some factors may increase the risk, while others may lower it. There are sections on How common stomach cancer is Age Diet Helicobacter pylori infection Smoking and alcohol Having polyps in your digestive system Other medical conditions Anti inflammatory drugs Family history Having other cancers Radiation exposure Reduced immunity Body weight Hormone replacement therapy (HRT) Work chemicals How common stomach cancer is Stomach cancer is now the 10th most common cancer amongst adults in the UK. About 7,700 cases are diagnosed each year. Out of every 100 cancers diagnosed, 3 are cancer of the stomach. It is nearly twice as common in men as it is in women. Age Age is a significant risk factor for stomach cancer. Like most cancers, it becomes more common with increasing age. 95 out of every 100 cases (95%) are diagnosed in people aged 50 or more. Diet The incidence of stomach cancer in the UK has fallen a great deal since the 1930s. This is probably partly due to better diet. Incidence varies from country to country around the world. This may be explained to some extent by differences in diet. A diet high in very salty foods increases the risk of stomach cancer. Stomach cancer levels are very high in Japan where very salty pickled foods are popular. But these foods are not typically eaten in the UK and stomach cancer rates here are lower than in Japan. A diet high in certain preserved foods may also increase your risk. A large ongoing research study called EPIC has found a significantly increased risk of stomach cancer in people who eat a lot of preserved meat, such as bacon, sausages and ham. The study found that this risk was greatest in people infected with Helicobacter pylori bacteria. Preserved meats contain chemicals called nitrosamines, which are known to cause Stomach cancer risks and causes 01
cancer in animals. Some studies show a higher risk of stomach cancer in people with high levels of nitrosamines in their diet. A diet high in fresh fruit and vegetables seems to reduce the risk of stomach cancer. This may be because these foods contain high levels of antioxidant vitamins. Vitamin C in particular, together with other substances in these fresh foods, may help to prevent damage to the stomach lining that can lead to cancer. Research studies have shown that antioxidant vitamins may have the greatest protective effect in people who are under nourished. Antioxident vitamins help in well nourished people too, but their effects are not likely to be so great. In the UK only about 1 in 8 men and 1 in 6 women eat enough fruit and vegetables - the recommended minimum of 5 portions a day. So there is a lot we can do to eat our way to a healthier life. If you are worried about cancer or heart disease, take a long hard look at your diet and see if you can improve it. Helicobacter pylori infection Helicobacter pylori is a bug that has been investigated a lot in the past few years. Infection with this type of bacteria increases the risk of stomach cancer in the lower part of the stomach. A recent study found that helicobacter pylori (HP) infection could double stomach cancer risk. Infection with a particular type of HP called 'caga positive helicobacter pylori' can increase the risk even more. Millions of people are infected with these bacteria and most of those do not get stomach cancer so other factors must also be at work. Diet and smoking may interact with HP to cause stomach cancer. The bug can cause an inflammatory condition called severe chronic atrophic gastritis (SCAG) and this can lead to stomach cancer. People with SCAG have an increased risk of stomach cancer in both the upper and lower parts of the stomach. Helicobacter infection can be shown on a blood test or a breath test. It can usually be cured fairly easily with a course of antibiotic treatment. But we're not really sure yet how much benefit we get from getting rid of it. So your doctor may not treat it unless you have stomach pains (a symptom of peptic ulcer). Even if you do have it treated, there is a chance that you will get reinfected because it is so common. Another reason not to treat HP is that it may protect against a particular type of cancer of the food pipe (oesophagus) called adenocarcinoma of the oesophagus. Smoking and alcohol Cigarette smoke contains many cancer causing chemicals. When you breathe in cigarette smoke, you will always swallow some of it without meaning to. In that way, smoking can increase the risk of stomach cancer. About 1 in 5 stomach cancers in Europe is thought to be caused by smoking People who smoke have twice the risk of stomach cancer compared to non smokers. The risk stays higher for 10 to 20 years after stopping smoking. If smokers have HP infection, they may have as much as 17 times the risk of non smokers without HP infection Alcohol on its own doesn't seem to increase stomach cancer risk. But regular drinking may increase the risk in smokers. Stomach cancer risks and causes 02
Having polyps in your digestive system A rare condition called FAP (familial adenomatous polyposis) may increase the risk of stomach cancer. This is an inherited condition (you are born with it) where many polyps grow throughout the digestive system. It is a known risk factor for bowel cancer. Most of these polyps are not serious and don't increase cancer risk. But a type of polyp called an adenomatous polyp can go on to develop into cancer. Another rare type of polyp called a leiomyoma can also develop into a type of cancer called a gastrointestinal stromal tumour (GIST). Other medical conditions Acid reflux is where acid from the stomach goes back up into the oesophagus. It can cause inflammation of the oesophagus (oesophagitis). Acid reflux and oesophagitis increase the risk of stomach cancer. Acid reflux is also called 'gastro oesophageal reflux disease' or GORD. Stomach cancer risk is increased in people who have severe GORD or who have had surgery to treat the resulting changes in the cells that line the food pipe. Changes to these cells are called Barrett's oesophagus. Some diseases and operations have been linked to increased stomach cancer risk because they lower the amount of acid produced in the stomach. These include Pernicious anaemia Having part of the vagus nerve removed (vagotomy) Having had part of your stomach removed (partial gastrectomy) The reduced acid level may allow more bacteria to grow and the bacteria may help to produce more nitrites and nitrosamines - chemicals that may increase stomach cancer risk. If you've had a stomach ulcer in the past, your risk of stomach cancer is doubled. But if you have surgery for a stomach ulcer, your risk of stomach cancer is lower than patients with a stomach ulcer who do not have surgery. If you've had a duodenal ulcer, your risk of stomach cancer is likely to be lower than average. This may be because duodenal ulcers are caused by too much stomach acid and the acid protects you against stomach bacteria. Anti inflammatory drugs Some studies seem to show that people who regularly take non steroidal anti inflammatory drugs appear to have a slightly lower risk of stomach cancer. These drugs are called NSAIDs. Examples are ibuprofen or Nurofen. This needs more research though, and regular use of NSAIDs can increase the risk of developing stomach or duodenal ulcers. Family history Family history is being looked at as a risk factor for stomach cancer. Brothers, sisters, and children, of people with stomach cancer have an increased risk of getting it themselves. We're not sure whether this is genetic, or because they share other risk factors, such as H pylori infection. Researchers have found Maori families from New Zealand who carry a particular faulty gene (mutated gene) more often than the general population. This changed gene makes developing stomach cancer more likely. A person from one of these families with the gene mutation has a 70% chance of getting stomach cancer at some point in their life. Often, people with this mutation Stomach cancer risks and causes 03
who get stomach cancer are younger - in their 30's rather than their 70's (which is a more usual age for stomach cancer). It is early days for this research and we don't yet know if there are any other inherited genetic mutations for stomach cancer. Having other cancers Statistically, men have a slightly increased risk of stomach cancer if they've already had prostate cancer, bladder cancer or testicular cancer. Women have an increased stomach cancer risk if they've had ovarian cancer, breast cancer or cervical cancer. Both sexes have increased risk if they've had food pipe (oesophageal) cancer, non melanoma skin cancer, bowel cancer or non Hodgkin's lymphoma. Radiation exposure Atomic bomb survivors in the 2nd World War were more likely to get stomach cancer because of the radiation they were exposed to. And we've known for many years that people who have had radiotherapy to the spine for a condition called ankylosing spondylitis have an increased risk. following an organ transplant, have double the risk of stomach cancer compared to other people. Body weight Studies show that people with a higher body mass index have an increased risk of adenocarcinoma in the upper area of the stomach. Being overweight increases the risk of acid reflux and gastric oesophageal reflux disease, which increase the risk of stomach cancer. Hormone replacement therapy (HRT) One study has shown that in women who take hormone replacement therapy (HRT) their risk of stomach cancer is half that of women who do not take HRT. Work chemicals Some studies show a higher risk of stomach cancer in people who are exposed at work to dust from metal, mining, quarrying or stone cutting. Stomach cancer has also been linked to medical X-ray exposure in the past. These days, the amount of radiation used in a regular X-ray is much lower than it used to be. But some other medical tests, such as CT scans, use a significant amount of radiation. This is not harmful to you if you have scans only when you need them. But it explains why doctors are reluctant to use scans for routine screening. Reduced immunity There is evidence that people with suppressed immune systems due to infection with HIV, AIDS, or drugs taken Stomach cancer risks and causes 04
Notes More information For more information about stomach cancer, visit our website http://cancerhelp.cancerresearchuk.org You will find a wide range of detailed, up to date information for people affected by cancer, including a clinical trials database that you can search for cancer trials in the UK. You can view or print the information in a larger size if you need to. For answers to your questions about cancer call our Cancer Information Nurses on 0808 800 4040 9am till 5pm Monday to Friday Adapted from Cancer Research UK s Patient Information Website CancerHelp UK in July 2010. CancerHelp UK is not designed to provide medical advice or professional services and is intended to be for educational use only. The information provided through CancerHelp UK and our nurse team is not a substitute for professional care and should not be used for diagnosing or treating a health problem or disease. If you have, or suspect you may have, a health problem you should consult your doctor. Cancer Research UK 2010. Cancer Research UK is a registered charity in England and Wales (1089464) and in Scotland (SC041666). Stomach cancer risks and causes 05