Causes and risk factors of womb cancer
There are certain things that can increase the risk of developing womb cancer. These are called risk factors. Having a risk factor does not mean you will get cancer. And not having a risk factor does not mean that you will not get it. Most risk factors for womb cancer are linked to how much oestrogen the lining of the womb is exposed to over your lifetime.
Before the menopause, the ovaries produce the hormones oestrogen and progesterone. These help to control your periods. After the menopause, the ovaries no longer produce hormones, but some oestrogen is still produced by body fat and adrenal glands.
The risk of womb cancer can be affected by:
- exposure to oestrogen
- how this is balanced with progesterone.
When there is too much oestrogen without progesterone to balance it, the risk of womb cancer increases.
Longer exposure to oestrogen can increase your risk of womb cancer. This may be influenced by the following factors:
- Starting your periods early (before the age of 12).
- Having a late menopause (after the age of 55).
- Having longer periods.
- Having irregular periods.
- Having some type of hormone replacement therapy (HRT), for example oestrogen only HRT.
- Not having children, or being unable to have children. Oestrogen in the body is low during pregnancy, and the level of progesterone is high.
Being overweight is an important risk factor for womb cancer. After the menopause, body fat is the main source of oestrogen. If you are overweight, you may have a high level of oestrogen.
At least 1 in 3 womb cancers (33%) may be caused by being very overweight (obese). There is also evidence that being less physically active can increase the risk of womb cancer.
A small number of womb cancers (fewer than 5 in 100 or less than 5%) are caused by gene changes that are passed on in a family. If there are several close relatives on the same side of the family with bowel, breast, ovarian or womb cancer, there may be a genetic link. Close relatives include parents, children, sisters and brothers.
If you are worried about a family history of cancer, speak to your cancer doctor or GP. They can decide if you should be referred to a family cancer clinic.
There are some genetic conditions that can increase the risk of womb cancer. Women with Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), have an altered gene that increases the risk of bowel cancer and womb cancer. Women with this gene have a 30 to 60% risk of developing womb cancer over their lifetime. They are screened for bowel cancer and womb cancer. And they may be advised to have a hysterectomy (operation to remove the womb) if they no longer want to be able to get pregnant.
Women with a rare genetic condition called Cowden syndrome have an increased risk of non-cancerous tumours and also some cancers. This includes womb cancer, but the increase in risk is small.
Tamoxifen is a hormonal drug used to treat breast cancer. It can slightly increase the risk of pre-cancerous changes in the womb. Rarely, it can cause womb cancer. But there are very clear benefits of taking tamoxifen that far outweigh this risk. Always tell your doctor if you are taking tamoxifen and have any unusual vaginal bleeding.
Some other medical conditions may cause an increased risk of pre-cancerous changes in the womb or womb cancer.
Thickening of the womb lining
Thickening of the lining of the womb is called endometrial hyperplasia. Symptoms include heavy periods and bleeding between periods or after the menopause. When it is diagnosed, women have treatment or regular check-ups.
Diabetes increases the risk of womb cancer. There may also be a separate link between womb cancer and insulin, a hormone that regulates blood sugar.
Polycystic ovary syndrome (PCOS)
PCOS is a condition where cysts grow on the ovaries. Women with PCOS may:
- have fertility problems, infrequent periods or no periods
- be very overweight or diabetic.
These are all linked with womb cancer risk.
Uncommon ovarian cancers
Some types of ovarian cancers called granulosa and theca cell tumours can produce oestrogen. This increases the risk of pre-cancerous changes and rarely can cause womb cancer.