Causes and risk factors of stomach cancer
The exact cause of stomach cancer is unknown, but risk factors can increase the chance of a person developing it.
What are risk factors?
Certain things can increase the chance of developing stomach cancer. These are called risk factors. Having a risk factor does not mean you will definitely get stomach cancer. Or if you do not have any risk factors, you may still be diagnosed with stomach cancer. We do not yet know why only some people who have risk factors develop stomach cancer.
Stomach cancer is not infectious and cannot be passed from one person to another.
If you are worried about stomach cancer and would like to talk to someone, we're here. You can:
- Call the Macmillan Support Line for free on 0808 808 00 00.
- Chat to our specialists online.
Helicobacter pylori (H. pylori) infection
Helicobacter pylori (H. pylori) is a bacteria that lives in the lining of the stomach. H. pylori infection is common. For most people, it will not cause any problems. But sometimes, it can cause the stomach to become inflamed and cause changes in the cells that line the stomach. Over time, these cells become abnormal and may become cancer.
Sex
Stomach cancer is more common in men than in women. Men are twice as likely as women to get stomach cancer.
Age
The risk of developing stomach cancer increases as you get older. Over half of people (50%) diagnosed with stomach cancer are aged 75 or older.
Diet
Diet can affect the risk of stomach cancer. These things can increase your risk:
- not eating enough fresh fruit and vegetables
- having too much salt in your diet
- eating a lot of processed meats
- eating foods that are smoked or pickled.
The number of people in the UK who develop stomach cancer is decreasing. This is probably because our diet is improving and we are eating more fresh foods.
Being overweight
People who are very overweight have an increased risk of cancer in the area where the stomach joins the oesophagus. This area is called the gastro-oesophageal junction (GOJ).
Stomach conditions
Some stomach conditions can increase the risk of developing stomach cancer.
Changes to the stomach lining
The following medical conditions can cause changes to the stomach lining and increase the risk of stomach cancer:
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Pernicious anaemia
This is when the immune system attacks cells lining the stomach that make intrinsic factor (IF). IF helps us absorb vitamin B12 and make red blood cells. If you are not making enough IF, you do not absorb enough vitamin B12, and have too few red blood cells (anaemia).
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Atrophic gastritis
This is a chronic inflammation of the stomach lining.
Stomach surgery for another condition (such as an ulcer)
Removing part of the stomach reduces the amount of acid your stomach makes. This means you have less protection from bacteria, which can increase the risk of stomach cancer.
Family history and risk of stomach cancer
Most stomach cancers are not caused by inherited cancer genes. Most people who develop stomach cancer do not have a strong family history of it.
But sometimes stomach cancer runs in families. This may be because close family members share some risk factors for stomach cancer. For example, they may eat a similar diet or have H. pylori infection. Rarely, it is caused by an inherited gene.
In general, the chance of a family link is greater when:
- a number of family members have been diagnosed with stomach cancer
- these family members are closely related
- they were diagnosed with stomach cancer at a younger age.
About our information
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.
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References
Below is a sample of the sources used in our stomach cancer information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk
Lordick F, Carneiro S, Cascinu T, Fleitas K, Haustermans G, Piessen A, et al. Gastric cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Annals of Oncology. 2022;33(10): 1005–1020. Available from www.doi.org/10.1016/j.annonc.2022.07.004 [accessed July 2023].
National Institute for Care and Health Excellence. Oesophago-gastric cancer: assessment and management in adults NICE guideline [NG83]. 2018. Available from www.nice.org.uk/guidance/ng83 [accessed July 2023].
Dr Chris Jones
Reviewer
Speciality Registrar in Clinical Oncologist and Clinical Lecturer in Clinical Oncology
Date reviewed
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