Womb cancer risks and causes
This page tells you about the possible causes and risk factors for womb cancer. There is information about
How common womb cancer is
Womb cancer is now the 4th most common cancer in UK women. It is most common among women between the ages of 60 and 69.
Risk factors for womb cancer
We don't know exactly what causes womb cancer. But there are some things that might increase the risk and others that seem to reduce risk. Overweight or obese women are generally more likely to develop womb cancer than women of a normal weight.
Factors related to your menstrual history can increase risk of womb cancer, including starting periods early and having a late menopause.
Having had a baby lowers your risk of womb cancer. If you have more than one child, you lower your risk even further.
You can view and print the quick guides for all the pages in the About womb cancer section.
This section of CancerHelp UK is about endometrial cancer, which is the most common type of womb cancer. The endometrium is the inner lining of the womb and all endometrial cancers start here. It is also called uterine cancer or cancer of the uterus. There is more information about rare types of womb cancer in this section of CancerHelp UK.
About 6,800 women are diagnosed with womb cancer in the UK each year. This is about 8 out of every 100,000 women. About 5 out of every 100 cancers diagnosed in women are womb cancers. This makes it the 4th most common cancer found in women in the UK. Womb cancer occurs most commonly in women aged 60 to 69 and is very rare in women who have not yet had their menopause.
We don't know exactly what causes endometrial womb cancer. But there are some things that might increase the risk of developing it. And there are other factors that seem to reduce the risk. Having a risk factor does not necessarily mean that you will develop cancer. Also, not having a risk factor does not necessarily mean that you will not develop cancer.
Many of the womb cancer risk factors are related to the body’s exposure to the female sex hormone, oestrogen. Or, more specifically, to the balance between types of the two female sex hormones oestrogen and progesterone. Oestrogen without progesterone to balance it increases risk of womb cancer. Doctors call this 'unopposed oestrogen'. The body stops making progesterone after the menopause, but still produces a small amount of oestrogen. So this explains why womb cancer is much more common in women after menopause.
Most women diagnosed with womb cancer are past their menopause. It occurs most commonly in women between the ages of 60 and 69. About 93 out of every 100 cases occur in women over 50, with the average age at diagnosis in the UK being 63. Fewer than 1 in 20 cases (5%) are diagnosed in women under 40. But women who have a particular gene fault called HNPCC are more likely than the general population to develop it at a younger age.
Women who are obese are generally 2 or 3 times as likely to develop womb cancer than women of a normal weight. Women who are very obese may increase their risk by up to 6 times. This is probably because fatter women have higher levels of oestrogen. Fat cells (also called adipose tissue) convert certain hormones into a form of oestrogen. So the more body fat you have, generally the more oestrogen you produce. The more oestrogen being produced, the more the lining of the womb is built up. When more lining (endometrial) cells are produced, there is a greater chance of one of them becoming cancerous.
Another reason for the higher risk of womb cancer in overweight women may be related to insulin. Insulin helps the body unlock and use the energy in food that we eat. People who are overweight can sometimes become resistant to insulin. This means that although the body can produce insulin, the insulin doesn’t work as well as usual. To make up for this, the body makes too much. Some studies show that having higher levels of insulin is linked with an increased risk of womb cancer. This may be because the extra insulin can stimulate cancerous growth in the lining of the womb.
Diet only seems to play a small role in in womb cancer. If you eat a high fat diet you may have a higher risk of developing womb cancer. We don’t know whether this is directly to do with the fat in your diet, or whether it is because eating more fat tends to make you overweight.
Some studies have reported a lower risk of womb cancer in women who eat a lot of isoflavones (found in soya based foods). Isoflavones are part of a group of plant chemicals known as phyto-oestrogens. They can behave like the female hormone oestrogen and have similar effects on the body.
Coffee has been shown to reduce womb cancer risk, although more studies are needed to clarify this relationship.
There is some evidence that fibre in the diet and higher intake of vegetables reduces womb cancer risk. But some studies have not shown a link and we need more research to be sure.
A recent study showed that women who drank 3 or more units of alcohol a day had double the risk of womb cancer compared to women who did not drink at all. Earlier studies have not shown an association with alcohol consumption so we need more research to clarify this.
Having had a baby lowers your risk of womb cancer. Studies seem to show that having one child lowers your risk by about a third. Different studies give different figures but if you have 3 or more children your risk could be lowered by up to two thirds. Oestrogen levels are low and progesterone levels are high in pregnancy. Normally, at times during your menstrual cycle, there is oestrogen in your body without progesterone to balance it. Doctors call this 'unopposed oestrogen'. High levels of oestrogen (unopposed oestrogen) increases the risk of womb cancer. Anything that stops this, even for a few months, lowers the risk of womb cancer. If you have never been pregnant you are more likely to develop womb cancer than if you have had children.
Some factors linked with periods (menstruation) can increase your risk of womb cancer because they cause higher levels of oestrogen. Examples are
- Irregular bleeding during and after the menopause
- Infertility due to failure of the ovaries
- A late menopause (after the age of 52)
- Failing to ovulate (release an egg every month)
- Not having periods, or not having them often
- Having longer than average periods
- Starting your periods early
All these factors can contribute to your risk of womb cancer.
Endometrial hyperplasia is a benign condition where the lining of the womb becomes thicker. If you have this thickening you have a higher risk of developing womb cancer, especially if the extra lining cells are abnormal. Symptoms of endometrial hyperplasia are heavy periods, bleeding between periods, and bleeding after menopause. Your doctor may advise a ‘D and C’ if you have these symptoms. This stands for dilation and curettage. It means opening up the cervix and scraping away the extra cells from inside the womb. These are then examined under a microscope to see if they are abnormal or not.
Polycystic ovary syndrome (PCOS) is also called Stein-Leventhal syndrome and is a condition where cysts grow in the ovaries. Women with PCOS have a hormone imbalance. This can cause infrequent periods, lack of periods, and fertility problems. Women with PCOS are also more likely to be insulin resistant, overweight, and have diabetes and high blood pressure. They have an increased risk of womb cancer compared to women who don’t have PCOS. But this may be because all the symptoms are also risk factors for womb cancer.
If you have had cancer of the colon, rectum or breast in the past, you are at a slightly increased risk of getting womb cancer. Similarly, once you have had womb cancer, you have a slightly increased risk of developing certain other cancers.
Research has shown that women with mothers who have womb cancer have double the risk of women in the general population.
Most cancers are 'sporadic'. That means they are not caused by a gene that you inherited. But some cancers are caused by cancer genes that you were born with. If you have several close relatives on the same side of the family who have had bowel cancer or womb cancer you may be at increased risk of womb cancer because of a faulty gene. But even if there is a faulty gene in your family, you may not have inherited it.
Hereditary nonpolyposis colon cancer (HNPCC) is an inherited faulty gene associated with an increased risk of a variety of cancers, especially bowel cancer. This condition is also sometimes called Lynch syndrome. Other than bowel cancer, womb cancer is the most common cancer linked with this syndrome. Out of every 100 women who carry the HNPCC gene fault, 60 will develop womb cancer at some point in their lives. In this group of women, womb cancer tends to start at a younger age than in the general population. About 1 in 6 womb cancers in women with the HNPCC gene fault are diagnosed before age 40. But it is important to remember that womb cancers in these women are often picked up at an early stage and so are more likely to be cured.
An increased risk of womb cancer is a known side effect of taking tamoxifen, which is a hormonal therapy for breast cancer. Scientists think this is because the drug has a similar effect on the womb to oestrogen. If you have been taking tamoxifen for more than two years or so, you may be monitored for possible signs and symptoms of womb cancer. The major sign to look out for is unexpected bleeding. It is important to tell your doctor if your periods have stopped, but you have any vaginal bleeding while you are taking tamoxifen.
Raloxifene, another hormonal treatment for breast cancer, has also been shown to increase breast cancer risk in one study, but the picture is not clear, because another study showed a reduction in womb cancer risk in women who took Raloxifene.
Remember - If you have had breast cancer, the benefits of taking tamoxifen to prevent your breast cancer coming back are far more important than the small risk of getting womb cancer.
Hormone replacement therapy is used by many women to control symptoms associated with menopause. There are different types of HRT. Oestrogen only HRT increases the risk of womb cancer and is normally only prescribed to women who have had their womb removed (a hysterectomy). And one of the studies shows a small reduction in risk of womb cancer in women taking continuous combined HRT. However, women also need to take into account the risk of other cancers when choosing whether to take HRT. Women taking combined HRT have a slightly increased risk of breast cancer. So if you are considering using HRT you need to discuss the risks and benefits of the treatment with your doctor.
Most types of birth control pills used today normally decrease the risk of womb cancer. These contain either a combination of oestrogen and progesterone (combination pills), or progesterone only (mini-pills).
Diabetes and high blood pressure are both linked to being overweight and so may be connected with womb cancer for that reason. But several studies show a higher risk of womb cancer in women with diabetes, even after taking bodyweight into account.
Some studies show a reduced risk of womb cancer for women who are more physically active. But other studies do not show a reduced risk. So any link may just be because physically active women have a lower bodyweight.
White women have a greater chance of developing womb cancer than black women. But if black women do get womb cancer, these cancers are more likely to be aggressive (fast growing) tumours. The reason is not known but it may be due to genetic differences. Womb cancer is quite common in Jewish women and the highest incidence is in white women living in the USA. It is much less common in Japan, India and Africa.
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