Updated 8 August 2008
Risk Factors:
Cancer of the uterine cervix is the ninth most common cancer in BC women with an incidence rate of 9.8 per 100,000. Over 80% of all cervical cancer cases are squamous cell carcinomas arising in the ectocervix with further 17% being adenocarcinoma or adenosquamous carcinoma arising in the endocervical canal. The incidence rate has been steadily falling for several decades with an average annual rate of decline of about 2% (National Cancer Institute of Canada, 1998). Cervical cancer responds well to treatments, resulting in a 5-year relative survival of about 74%.
Human papillomaviruses (HPV) infection, particularly with one of several particular virus subtypes, is the major factor causally associated with cervical cancer. Several studies have observed relative risks ranging from 4 to 40 folds (Kelsey and Whittemore, 1994). There is evidence of positive relationships between cervical cancer risk and early age of first marriage, early age of pregnancy, greater number of sexual partners, as well as early age of first intercourse. The relationship with lifetime number of sexual partners appears weakened when HPV infection is taken into account.
Higher risks of cervical cancer have been observed for long-term or high-intensity smokers. However, in many recent studies, the effect of smoking has practically disappeared when HPV infection is taken into consideration.
HIV infection in women also appears to elevate risk of cervical cancer.
Prevention:
The early detection of precancerous lesions, through the Papanicolaou (Pap) smear, can basically prevent invasive squamous cell carcinoma of the cervix. This test was introduced in Canada in the mid-1960s and is widely used in BC. A recent Canadian workshop (Miller et al, 1991) recommended re-screening every three years, after two annual normal smears, for women age 18-69; in the context of an organized screening program.
Prevention of transmission of HPV infection appears to be unfeasible currently. Condom use cannot completely prevent the spread of HPV genital infections because the genital HPV infections are not restricted to the penile skin (Kelsey and Whittemore, 1994).
There is now a vaccine which protects against 2 types of Human Papillomaviruses that cause most cervical cancers.The vaccine is recommended for girls and women between the ages of 9 and 26 years before they come in contact with HPV. The vaccine may also benefit women who are sexually active and have not yet been infected with HPV. The vaccine prevents HPV infection but it does not get rid of it once the infection occurs.
In women who have never been infected with HPV, the vaccine:
- Protects against 7 out of 10 cases of cancer of the cervix.
- Is safe, very effective and has few side effects.
For more information call your local Public Health Unit or speak to your Family Physician. You can also go to http://www.immunizebc.ca/ or to http://www.bchealthguide.org/healthfiles/hfile101.stm
References:
- National Cancer Institute of Canada. Cancer Statistics, 1998. NCIC, Toronto.
- Kelsey J, Whittemore AS. Epidemiology and primary prevention of cancers of the breast, endometrium and ovary: a brief overview. Ann Epidemiology 1994;4:89-95.
- Miller AB, Anderson G, Brisson J, et al. Report of a national workshop on screening for cancer of the cervix. Can Med Assoc J 1991;145:1301-1325.