SUPPORT CANADIANS LIVING WITH CANCER
Risk factors for uterine cancer
A risk factor is anything (such as a behaviour, substance or condition) that increases the risk of developing cancer. Most cancers are the result of many risk factors, but sometimes uterine cancer develops in women who don’t have any of the risk factors described below.
Post-menopausal women aged 45–70 years have the highest risk of developing uterine cancer. It is more common in Caucasian women than in other populations. Women living in North America or Europe develop uterine cancer more often than those living in other parts of the world. Women in higher income groups also tend to be affected more often than women in lower income groups.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
|Known risk factors||Possible risk factors*|
*You may wonder about intrauterine devices (IUDs). There is significant evidence showing that there is no association between IUDs and uterine cancer.
Known risk factors
There is convincing evidence that the following factors increase your risk for uterine cancer.
Hormone replacement therapy (HRT)Hormone replacement therapy (HRT)Treatment that replaces female sex hormones ( estrogen, progesterone or both) when they are no longer produced by the ovaries. is used to manage the symptoms of menopause, such as hot flashes, vaginal dryness and mood swings. Research shows that using estrogen alone, without progesterone, as an HRT increases the risk of uterine cancer. Taking estrogen combined with progesterone (combined HRT) does not increase a woman’s risk of uterine cancer.
Women who are overweight or obese have a higher risk of developing uterine cancer. Being more than 50 pounds over the ideal body weight makes it about 10 times more likely that you will develop uterine cancer.
Researchers don’t know the exact reason why being overweight or obese increases the risk. Having too much fat tissue raises the level of estrogen in the body, and too much estrogen increases the risk of uterine cancer. Obese people often have higher levels of insulin and insulin-like growth factor-1 in their blood, which can help some tumours grow. The risk of uterine cancer is even higher in overweight or obese women who have hypertension or diabetes.
Early menstruation, or early menarche, is when your period (menstruation) starts before the age of 12. Late menopause is when your period stops after the age of 55. Both early menstruation and late menopause mean that your body makes estrogen for a longer period of time, which increases your risk of developing uterine cancer.
Tamoxifen (Nolvadex, Tamofen) is a drug used to treat breast cancer. Women who are treated with this drug for 5 or more years have a higher risk of developing uterine cancer.
Women who have never given birth to a child are 2 times more likely to develop uterine cancer as women who have given birth at least once. During pregnancy, estrogen levels in the body are lowered. The more times a woman gives birth, the lower her risk of developing uterine cancer.
Polycystic ovarian syndrome is caused by changes to normal hormone cycles and the normal ovulation process. Many women with polycystic ovaries have few periods, or none at all, and may have difficulty getting pregnant. Women with polycystic ovary syndrome have a higher risk of developing uterine cancer.
Endometrial hyperplasia is an overgrowth of normal cells that line the uterus. It tends to progress to atypical endometrial hyperplasia, which is an overgrowth of abnormal cells that can become cancer. When untreated, approximately 1.6% of endometrial hyperplasias and 23% of atypical hyperplasias become uterine cancer.
Radiation therapy is used to treat other cancers or bleeding from the uterus caused by a benign (non-cancerous) condition. Women who have received high-dose radiation to the pelvis have a higher risk of developing uterine cancer.
Diabetes increases the risk of uterine cancer. A woman is at even higher risk if she is also obese or has high blood pressure (hypertension).
Ovarian tumours that make estrogen are called estrogen-secreting tumours. Women with estrogen-secreting ovarian tumours have a higher risk of uterine cancer due to the higher estrogen levels.
Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) is an uncommon genetic condition that affects mismatched repair genes. These genes normally correct mistakes when DNADNASee deoxyribonucleic acid (DNA). is copied during cell division. With Lynch syndrome, mismatched repair genes don’t work properly and cells with genetic mistakes are not repaired. Eventually, these abnormal cells build up and can become cancerous.
Women with Lynch syndrome have a greater risk of developing uterine cancer in their lifetime. Women with Lynch syndrome tend to develop uterine cancer before the age of 45, which is much younger than women in the general population.
The following factors have been linked with uterine cancer, but there is not enough evidence to say they are known risk factors. Further study is needed to clarify the role of these factors for uterine cancer.
A few studies have looked at a woman’s risk of developing uterine cancer if she has one or more first-degree relatives (mother, sister or daughter) who have had uterine cancer. At present, researchers don’t know if the connection between having a family history of uterine cancer and developing uterine cancer is due more shared genes or to shared environment and behaviours among female family members.
High blood pressure
High blood pressure, or hypertension, appears to increase the risk of uterine cancer. A woman may be at even higher risk if she is also obese or has other risk factors.
Researchers have found that a history of gallbladder disease increases the risk of developing uterine cancer. The risk may be from factors linked to gallbladder disease, such as obesity and the use of estrogen replacement therapy, rather than gallbladder disease itself.
Inherited cancer syndromes
Studies have shown more cases of uterine cancer in women who have or are at risk for certain inherited syndromes. These include Cowden syndrome, which is a mutation in the tumour-suppressor gene PTEN, and a p53 gene mutation.
Diethylstilbestrol (DES) exposure
DES is a form of estrogen. Between 1940 and 1971, DES was used to treat women who had certain problems during pregnancy, such as miscarriage. It has not been approved for use in pregnant women since the 1970s.
Daughters of women who took DES during their pregnancy may have a higher than average risk of developing uterine cancer.
Studies have shown that women who eat a diet with high glycemic load have a higher risk of uterine cancer. Glycemic load is a measure of how much a food increases your blood sugar and insulin levels. The higher a food’s glycemic load, the more it increases blood sugar and insulin levels. A diet high in glycemic load can raise your blood sugar and insulin levels, which can cause cancer to grow. A diet high in sugary foods, sugary drinks and processed foods high in carbohydrates will have a high glycemic load.
Studies show that greater physical activity is associated with a lower risk of uterine cancer. The research suggests that physical inactivity is probably a risk factor for uterine cancer.
There is some research that suggests a link between sedentary behaviour and increased risk of uterine cancer.
Unknown risk factors
It isn’t known whether or not the following factors are linked with uterine cancer. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if the following are risk factors for uterine cancer:
- environmental chemical exposure
- human papillomavirus (HPV) infection
- tall adult height
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about risks.