Cervical cancer is very common although rates vary around the world. Canadian women have a 1 in 153 chance of developing cervical cancer in their lifetimes.

HPV: a risk factor for cervical cancer

The most important factor that increases the risk of getting cervical cancer is infection with the human papillomavirus (HPV), the virus that causes genital warts. It is important to note that HPV has nothing to do with HIV, the virus that causes AIDS.

HPV is transmitted mostly through sexual contact. HPV is the most common sexually transmitted infection in Canada, and up to one-third of Canadian women may be infected with HPV.

There are over 100 variants of HPV, but only some are implicated in causing cervical cancer. Most HPV infections are "silent", that is, they produce no symptoms. When the HPV variants that are linked to cervical cancer do lead to symptoms, they tend to produce flat, hard-to-see genital warts around the vulva, cervix, and anus in women, around the penis, scrotum and anus in men. Easily visible genital or anal warts are not generally co-related with an increased risk of cervical cancer.

HPV infections are easy to contact - a recent study found that many young women contact HPV during their first sexual experience. Although condoms lower the risk of acquiring other STIs such as AIDS and gonorrhea, condoms are much less effective at preventing transmission of HPV, because skin-to-skin contact is enough to pass these on. In fact, in one study, most young women who contacted HPV had been using barrier methods of birth control, although for many of them, this was probably intermittent use.

Being in a monogamous relationship significantly lowers the risk of infection with HPV but does not entirely prevent it because the infection can lie dormant in a sexual partner for a long time, and suddenly become active again many years later.

Most HPV infections disappear without treatment because the body fights them off, and they do not go on to cause cancer. The current belief is that there must be other risk factors (such as smoking or the presence of other STIs) to enable HPV to produce cancerous changes.

Other risk factors for cervical cancer

There are many other risk factors for cervical cancer besides HPV.

Genes play a role in that a woman has a higher risk of cervical cancer if her sister or mother had it. As well, African-American women are more at risk that Caucasians.

Cervical cancer is more common in older women (although many older women don't realize that they are at risk), women with lower socio-economic status, and women smokers.

Sexual history is also very important. Women who have their first sexual contact at a younger age, women with more frequent sexual partners, women whose male partner has many sexual contacts, women who practice unprotected intercourse, and women with HIV are all at higher risk, in large part because of their higher risk of having an HPV infection. As well, research has found that another common sexually transmitted infection - chlamydia trachomatis - may also raise the risk of cervical cancer.

Diet also seems to play a role because cervical cancer is more common in women who eat diets low in fruits and vegetables. One study found a higher risk in women with low levels of vitamin E and coenzyme Q10.

Other possible risk factors include giving birth to many children, long-term use of oral contraceptives, and being the daughter of a mother who took DES (diethylstilbestrol, a medication used between 1940 and 1971 to treat women with certain problems during pregnancy).

Art Hister, MD 
in association with the MediResource Clinical Team