A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancer of the lung and many other cancers. But risk factors don't tell us everything. Having a risk factor, or even several, does not mean that you will get the disease. And not having any risk factors doesn't mean that you won't get it, either.
Scientists have found that certain risk factors make a woman more likely to develop vaginal cancer. Even if a woman with vaginal cancer has one or more risk factors, it is impossible to know for sure how much that risk factor contributed to causing the cancer. And many women with vaginal cancer do not have any apparent risk factors.
Age
Squamous cell cancer of the vagina occurs mainly in older women. Only 15% of cases are found in women younger than 40. Almost half of cases occur in women who are 70 years old or older.
Diethylstilbestrol (DES)
DES is a hormonal drug that was given to some women to prevent miscarriage between 1940 and 1971. Women whose mothers took DES (when pregnant with them) develop clear-cell adenocarcinoma of the vagina or cervix more often than would normally be expected. There is about 1 case of this type of cancer in every 1,000 daughters of women who took DES during their pregnancy. This means that about 99.9% of DES daughters do not develop this cancer.
DES-related clear cell adenocarcinoma is more common in the vagina than the cervix. The risk appears to be greatest in those whose mothers took the drug during their first 16 weeks of pregnancy. Their average age when they are diagnosed is 19 years. Since the use of DES during pregnancy was stopped by the FDA in 1971, even the youngest DES daughters are older than 35 -- past the age of highest risk. But there is no age when a woman is safe from DES-related cancer. Doctors do not know exactly how long women remain at risk.
DES daughters have an increased risk of developing clear cell carcinomas, but women don’t have to be exposed to DES for clear cell carcinoma to develop. In fact, women were diagnosed with this type of cancer before DES was invented.
DES daughters are also more likely to have high grade cervical dysplasia (CIN 3) and vaginal dysplasia (VAIN 3) when compared to women who were never exposed.
Vaginal adenosis
Normally, the vagina is lined by flat cells called squamous cells. In about 40% of women who have already started having periods, the vagina may have one or more areas where it is lined instead by glandular cells. These cells look like those found in the glands of the cervix, the lining of the body of the uterus (endometrium), and the lining of the fallopian tubes. These areas of gland cells are called adenosis. It occurs in nearly all women who were exposed to DES during their mothers' pregnancy. Having adenosis increases the risk of developing clear cell carcinoma, but this cancer is still very rare. The risk of clear cell carcinoma in a woman who has adenosis that is not related to DES is very, very small. Still, many doctors feel that any woman with adenosis should have very careful screening and follow-up.
Human papilloma virus
Up to 90% of vaginal cancers and pre-cancers (vaginal intraepithelial neoplasia -- VAIN) contain the human papilloma virus (HPV). HPV is a group of more than 100 related viruses. They are called papilloma viruses because some of them cause a type of growth called a papilloma. Papillomas -- more commonly known as warts -- are not cancers. Different HPV types can cause different types of warts in different parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.
Certain HPV types can infect the outer female and male genital organs and the anal area, causing raised, bumpy warts. These warts may barely be visible or they may be several inches across. The medical term for genital warts is condyloma acuminatum. 2 types of HPV, HPV 6 and HPV 11, cause most cases of genital warts. These 2 types are seldom linked to cancer, and so are called low-risk types of HPV.
Certain types of HPV have been strongly linked with vaginal cancers and pre-cancers. These types, HPV types 16 and 18, are considered high-risk types of HPV because they are strongly linked to cancer. They can also cause cancers of the cervix and vulva in women, cancer of the penis in men, and anal and oral cancers (in men and women).
HPV is passed from one person to another during skin-to-skin contact with an infected area of the body. Although HPV can be spread during sex -- including vaginal intercourse, anal intercourse, and oral sex - sex doesn't have to occur for the infection to spread. All that is needed is skin-to-skin contact with an area of the body infected with HPV. Infection with HPV seems to be able to be spread from one part of the body to another - for example, infection may start in the cervix and then spread to the vagina.
The only way to completely prevent anal and genital HPV infection is to never allow another person to have contact with those areas of the body.
Infection with HPV is common, and in most people the body is able to clear the infection on its own. In some, however, the infection does not go away and becomes chronic. Chronic infection, especially with high-risk HPV types, can eventually cause certain cancers, including vaginal cancer.
In women, HPV infections occur mainly at younger ages and are less common in women over 30. The reason for this is not clear. A person can be infected with HPV for years without any symptoms, so the absence of visible warts cannot be used to tell if someone has HPV. Even when someone doesn't have warts (or any other symptom), he (or she) can still be infected with HPV and pass the virus to somebody else.
Vaccines have been developed to help prevent infection with some types of HPV. Right now, 2 different HPV vaccines have been approved for use in the United States by the Food and Drug Administration (FDA): Gardasil® and Cervarix®. These are discussed in more detail later in this document.
Cervical cancer
Having cervical cancer or pre-cancer (cervical intraepithelial neoplasia or cervical dysplasia) increases a woman's risk of vaginal squamous cell cancer. This is most likely because cervical and vaginal cancers have similar risk factors, such as HPV infection and smoking.
Some studies suggest that treating cervical cancer with radiation therapy may increase the risk of vaginal cancer, but this was not seen in other studies, and the issue remains unresolved.
Smoking
Smoking cigarettes more than doubles a woman's risk of getting vaginal cancer.
Alcohol
Drinking alcohol might affect the risk of vaginal cancer. A study of alcoholic women found more cases of vaginal cancer than was expected. But this study was flawed because it didn't look at other factors that can alter risk, such as smoking and HPV infection. A more recent study that did take these other risk factors into account found a decreased risk of vaginal cancer in women who do not drink alcohol at all.
Human immunodeficiency virus
Infection with HIV (human immunodeficiency virus), the virus that causes AIDS, also increases the risk of vaginal cancer.
Vaginal irritation
In some women, stretching of the pelvic ligaments may cause the uterus to sag into the vagina or even extend outside the vagina. This condition is called uterine prolapse and can be treated by surgery or by wearing a pessary, a device to keep the uterus in place. Some studies suggest that long-term (chronic) irritation of the vagina in women using a pessary may slightly increase the risk of squamous cell vaginal cancer. But this association is extremely rare, and no studies have conclusively proven that pessaries actually cause vaginal cancer.
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