What Causes Cervical Cancer?
Almost all cervical cancers are caused by an infection with the sexually transmitted human papilloma virus (HPV).
HPV and Cervical Cancer
HPV can be transmitted through close skin to skin contact, usually during sexual activity. There are over 100 types of HPV, and only certain types will cause cancer. Other HPV types cause genital or skin warts. The body’s immune system will naturally clear most types of HPV, often within two years. HPV usually causes no symptoms. This makes HPV a common virus as most people can contract HPV and pass it on without knowing. Up to 90% of people who have been sexually active at least once will be infected with at least one genital type of HPV in their lives.
If the body does not clear the infection and it becomes persistent, high-risk HPV types can cause changes to cells in the cervix which may develop into cervical cancer. It usually takes 10-15 years for HPV to develop into cervical cancer, although in rare cases it happens more quickly. Only a small proportion of women with HPV go on to develop cervical cancer. In Australia, cervical cancer has become less frequent, with just under 900 patients diagnosed each year.
Cervical Cancer Risk Factors
Risk factors are characteristics that increase a person’s likelihood of developing a disease, such as a cervical cancer. There are different types of risk factors; some can be modified (diet, smoking, physical activity) while others can’t (age, genetic factors).
Although certain factors can increase a woman's risk for developing cervical cancer, they do not always cause the cancer. Many women carry at least one risk factor but still will not develop cervical cancer. Even if a woman with cervical cancer carries a risk factor, it is difficult to know how much that risk factor contributed to the development of cancer.
Risk factors include:
- HPV infection.
- Smoking. Women who smoke are approximately twice as likely as non-smokers to get cervical cancer.
- Not participating in regular Cervical Screening Tests.
- Age. Cervical cancer is more common in younger women. Around 70% of cervical cancers are diagnosed in women under 60 years old. However, people under 20 years of age rarely develop this cancer.
- Long-term use of the oral contraceptive pill is associated with a small increased risk of cervical cancer. This risk decreases if a person stops taking the pill. However, the pill has a substantial (50%) and long-lasting protective effect against ovarian and endometrial cancer.
- Previous abnormality or cancer of the cervix.
- Sexual history including becoming sexually active at a young age and having many sexual partners. However, HPV can also be transmitted the first time a person is sexually active, or in people with only one partner.
- Past or current chlamydia infection, which may help HPV grow.
- People who are immunocompromised (for example, people with HIV, AIDS, or organ transplant recipients) are at an increased risk of HPV infection.
- Early age of childbirth. Cancer Research UK reports experiencing childbirth before the age of 17 gives a higher risk, compared to women who had their first baby after the age of 25. The reasons for this are unclear.
- Having given birth to three or more children.
- Exposure to diethylstilbestrol (DES) in the womb. DES is a synthetic form of the hormone estrogen. Doctors prescribed DES to help some pregnant women to prevent miscarriage between the 1940s and 1970s in Australia. Women whose mothers were given DES during pregnancy may be at increased risk of cervical and also vaginal cancer. DES-related cervical cancers are less likely related to Human Papilloma Virus.
It is important for women to know their risk factors and talk about them with health professionals if concerned. Knowing cancer risk factors can prompt an individual to make lifestyle choices that may decrease cancer risk and improve overall health.
How to reduce Cervical Cancer risk
Cervical cancer is one of the most preventable types of cancer. Factors that may lower your risk of developing cervical cancer include:
- Intrauterine device (IUD) use
- HPV vaccination
- Regular cervical cancer screening tests every 5 years
- Abstinence from cigarette smoking
- Avoiding genital infections
The best way for women to protect themselves against cervical cancer is to have the HPV vaccine when aged 12–13 years. Since 2007 in Australia, women can be vaccinated against HPV, reducing the risk of both infection and cervical cancer. However, the HPV vaccine is not 100% effective. It covers nine HPV strains and in the long term will reduce the risk of cervical cancer by 90% (but not 100%).
To help prevent cervical cancer, regular Cervical Screening Tests after age 25 years is important. Early stage-cancers have a good survival rate and are highly treatable.
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