Guest Author - Denise Howard, M.D., M.P.H.

Cervical cancer is a malignancy of the cervix which is known to result from sexual exposure to a virus called Human Papilloma Virus (HPV). Once the cells of the cervix are infected it is possible for the body to fight the infection however in some cases the cervix may undergo precancerous changes and eventually develop cancer. This process can take 10 or more years. These viruses can also cause of malignancies of the vulva, vagina, anus and penis as well as a condition called recurrent respiratory papillomatosis.

The institution of routine Pap test has reduced the incidence of cervical cancer by 70% over the past 40 years but it still remains a problem. It is the second most common cancer in women worldwide. It has been estimated that there are over 500,000 new cases worldwide each year. It is estimated there will be 9600 new cases of cervical cancer and 3700 deaths in the U.S. attributed to this malignancy in 2006.

The Pap smear collects a sample of cells from the cervix. Cytologic examination allows identification of any potential abnormalities. It is important to remember that the Pap is a screening test. Screening test tend to over call abnormalities with the goal of not overlooking any true abnormalities. The consequence is that there will be many reported abnormal Pap smears that further testing yields normal cervical findings. On the other hand the Pap smear is unlikely to miss cervical abnormalities.

Precancerous changes are described as dysplasia and are categorized as low grade or high grade lesions. The low grade lesions are likely to regress while the high grade ones are associated with persistent HPV infection and thus are at greater risk of developing into cancer.

Thirty-five of the over 100 HPV types are known to infect the genital tract. Types are categorized as being high risk due to their strong association with cervical and anogenital cancers. HPV types 16, 18, 45 and 31 causes 65% of the cases of high grade lesions. Types 16 and 18 have been implicated in 70-80% of the cases of cervical cancer and 31 and 45 with another 5%. Types 6 and 11 are generally associated with low grade lesions but causes 80-90% of the cases of genital warts.

Over 20 million adults in the U.S. are infected with the Human Papilloma Virus. It is estimated that the acquisition rate for sexually active adults will be 6.2 million per year. Seventy-five percent of all sexually active adults will become infected at some point in their life. Women, especially younger women are more likely to be infected and it is estimated that 40% of them will become infected within 3 years of becoming sexually active.

The vast majority of HPV infections resolve own their own. Over a period of 30 months 60-75% will regress. Of women with high risk HPV types 15-30% will develop high grade lesions within 4 years and the rate of progression to invasive cancer is 1.44% during a 2 year period.
Fortunately, strategies for cervical cancer prevention are available. Pap smears are extremely effective in the early detection of cervical abnormalities. Treatments for dysplasia are effective and low risk. If detected early, even invasive cervical cancer can be successfully treated.

The identification of HPV has allowed the development of another weapon in the arsenal to prevent cervical cancer: a vaccination.