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Womb cancer is most often diagnosed in women between the ages of 60 and 79. We don't know exactly what causes it.  But there are some things that we know may increase risk and others that seem to reduce risk. 

Risk factors for womb cancer

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 the 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. 

 

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How common womb cancer is

This section is about the most common type of womb cancer - endometrial 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 also information about rare types of womb cancer in this section.

About 8,500 women are diagnosed with womb cancer in the UK each year. About 5 out of every 100 cancers diagnosed in women are womb cancers (5%). This makes it the 4th most common cancer in women in the UK.

 

What a risk factor is

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 any risk factors does not necessarily mean that you will not develop cancer.

Many of the risk factors for womb cancer relate to the body’s exposure to the female sex hormone, oestrogen. Or to the balance between types of the two female sex hormones, oestrogen and progesterone. Oestrogen without progesterone to balance it increases the 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 the menopause.

 

Age

Most women diagnosed with womb cancer have had their menopause. It occurs most commonly in women between the ages of 60 and 79. 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.

 

Being overweight

Women who are very overweight (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. A Cancer Research UK study published in 2011 found that being overweight or obese causes around a third of womb cancers. This is probably because fatter women have higher levels of oestrogen. Fat cells (also called adipose tissue) convert certain hormones into a type of oestrogen. So the more body fat you have, generally the more oestrogen you produce. When more oestrogen is produced the lining of the womb builds 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 to 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 produces insulin, the insulin doesn’t work as well as usual. To make up for this, the body makes too much. Some studies show that higher levels of insulin are linked to an increased risk of womb cancer. This may be because the extra insulin can stimulate cancerous growth in the lining of the womb.

 

Diet and alcohol

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 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. The way phyto oestrogens act is quite complex but they may block some of the effects of oestrogen. This seems to offer some protection from womb cancer. 

Coffee has been shown to reduce womb cancer risk, although we need more studies to be clear about this.

There is some evidence that fibre in the diet and a higher intake of vegetables reduces womb cancer risk. But some studies have not shown a link and we need more research to be sure.

Two recent analyses of studies showed no link between drinking alcohol and the risk of womb cancer.

 

Having had children or not

If you have never been pregnant you are more likely to develop womb cancer than if you have had children. 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. Unopposed oestrogen increases the risk of womb cancer. Anything that stops this, even for a few months, lowers the risk of womb cancer.

 

Menstrual history

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
  • Failing to release an egg every month (ovulate)
  • 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

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 procedure called a D and C if you have these symptoms. D and C stands for dilation and curettage. It means opening up the cervix and scraping away the extra cells from inside the womb. The cells are then examined under a microscope to see if they are abnormal or not. Instead of a D and C your doctor may advise a hysteroscopy  and a biopsy of the lining of the womb.

 

Polycystic ovary syndrome

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 which may cause very irregular periods. They are also more likely to be insulin resistant, overweight, and have diabetes. 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. A study in Australia showed that women under 50 who have PCOS have 4 times the risk of womb cancer than women of the same age who do not have PCOS.

Most women (more than 90%) who have  PCOS do not develop womb cancer.

 

Family history and other cancers

You are at a slightly increased risk of getting womb cancer if you have had cancer of the colon, rectum or breast in the past. Similarly, once you have had womb cancer, you have a slightly increased risk of developing certain other cancers.

Research has shown that daughters of women with womb cancer have double the risk of women in the general population.

Most cancers are not caused by a gene that you inherited. They are caused by gene changes in your lifetime as cells divide and grow to repair or replace old or damaged cells. Cancers due to these gene changes are called sporadic. 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 non polyposis colon cancer (HNPCC) is an inherited faulty gene associated with an increased risk of some 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, 40 to 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 the age of 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.

 

Tamoxifen and raloxifene

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 and you have any vaginal bleeding while you are taking tamoxifen.

Raloxifene, another hormonal treatment for breast cancer, has also been shown to increase womb 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.

If you have had breast cancer it is important to remember that the benefits of taking tamoxifen or other hormone therapies to prevent your breast cancer coming back are more important than the small risk of getting womb cancer.

 

Hormone replacement therapy (HRT)

Hormone replacement therapy is used by many women to control the symptoms of 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). 

Some studies show a small reduction in risk of womb cancer in women taking continuous combined HRT (containing oestrogen and progesterone). But a recent study looked at long term use of HRT. It found that normal weight women taking continuous combined HRT for 10 years or longer had an increased risk of womb cancer. Heavier women showed a slight reduction in risk with long term use of combined continuous HRT. We need further studies to check this. 

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.

 

Contraceptive pills

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).

 

Talcum powder

Regular use of talcum powder in the genital area may increase the risk of womb cancer. One study showed a 24% increase in postmenopausal women. But a more recent study in Australia did not show a link between the use of talcum powder in the genital area and womb cancer.

 

Diabetes and high blood pressure

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.

 

Physical activity

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. A recent Cancer Research UK study has shown that being inactive, causes just under 4 out of 100 womb cancers (4%). In the study, moderate activity was described as taking at least 30 minutes of exercise 5 times a week. This needs to be exercise that makes you slightly short of breath.  Any link may just be because physically active women have a lower bodyweight.

 

Ethnicity

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 faster growing tumours. 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. The reason for these differences is not known but it may be due to a combination of genetics and lifestyle.

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Updated: 14 January 2014