Cervical cancer is far less of a danger to American women than it was 50 years ago, thanks to screening with the Pap test. And it’s likely to become even less threatening over the next 50 years following the introduction of a vaccine that has the potential to prevent more than two thirds of all cases of invasive cervical cancer worldwide.
The cervix is the passage that leads from the vagina to the uterus. Cervical cancer is usually a slow process that starts with abnormal changes known as dysplasia. Eventually, cancer cells begin to form and spread more deeply into the tissue of the cervix and surrounding areas.
There are usually no symptoms, and, left undetected, cervical cancer was once a major cause of death for American women. It still is in many developing countries.
Thanks largely to increased use of the Pap test, the cervical cancer death rate in the United States fell by 74 percent between 1955 and 1992 and continues to decline at a rate of about 4 percent a year. In terms of saving lives, the Pap test is a notable success–the most effective of all cancer screening tests.
Another major advance came about two decades ago when strong links were found between cervical cancer and the human papillomavirus (HPV), usually manifested as genital warts. Of more than 100 types of HPV, most are harmless, but a few “high risk” types have been found in at least 99 percent of cervical cancers. Infection with HPV is now considered the number one risk factor for cervical cancer.
Today, a test to detect HPV is often used as a follow-up when abnormalities are detected on a Pap smear. It can also be used as a screening test on its own, and, in one recent study, it was nearly twice as effective as the Pap test in detecting early cervical cancer. Efforts to prevent HPV are central to the battle against cervical cancer.
The most recent breakthrough came in June of 2006 when the FDA approved Gardasil, a vaccine that has been found effective in preventing the two strains of HPV most frequently found in cervical cancer. As such, it’s the first anti-cancer vaccine. Cervarix, a similar vaccine, is expected to be approved in late 2007 or early 2008.
Gardasil has been found effective in preventing genital warts caused by HPV types 6 and 11 and in preventing precancerous cell changes caused by HPV types 16 and 18. Cervarix protects against HPV 16, 18, 31 and 45–types associated with cervical cancers.
Early Action Necessary
The catch is that the vaccines are effective only for prevention–before an abnormal Pap test occurs. For that reason, the American Cancer Society recommends that the vaccine be routinely administered to 11- and 12-year-old girls–or even as early as age 9, according to a doctor’s discretion. By immunizing females before sexual activity has started, health officials believe they can dramatically reduce the incidence of cervical cancer.
Catch-up vaccinations are also recommended for females age 13 to 18 who have not previously been immunized. Studies are being done to determine the benefit of immunization for adults age 18 and over. The vaccine cannot be used for treatment once precancerous changes have started to occur.
HPV is the most common sexually transmitted disease. An estimated 80 percent of women have been infected by age 50. It usually goes unnoticed and may clear on its own within a year or two.
Most genital warts are caused by low-risk types of human papillomavirus, and the high risk types often show no visible signs except for the precancerous changes in cervical cells.
HPV is difficult to prevent since it is passed by skin-to-skin contact as well as by sexual intercourse. While condoms provide some protection, the virus can be passed by contact with the skin of the genital or anal area that is not covered by a condom. Except for avoiding all genital contact with another person, there’s no sure way of avoiding an HPV infection.
Major risks for HPV, which are also risks for cervical cancer, include:
• having sex at an early age,
• having numerous sexual partners,
• having sex with someone who has had multiple sexual partners.
Young women, age 20 to 24, are most likely to be infected. And uncircumcised males tend to have a higher risk of passing along an infection.
Not all women who have had an HPV infection go on to develop cervical cancer. Other factors that make a woman vulnerable to cancer include:
SMOKING–Smokers have a risk double that of non-smokers. As with many other cancers, the combination of smoking with other risk factors may trigger cell changes that lead to cancer.
WEAKENED IMMUNITY: The immune system offers important protection against cancer. When immunity is weakened by illness or by HIV/AIDS, the risk of cervical cancer increases.
OTHER STDs: Infection with chlamydia, gonorrhea, syphilis (as well as HIV/AIDS) increases the risk of acquiring HPV and of developing cervical cancer.
MULTIPLE PREGNANCIES: The increased risk may result from greater sexual exposure and risk of HPV infection but also because of hormonal changes and weakened immunity during pregnancy.
LONG-TERM USE OF ORAL CONTRACEPTIVES: Women who used oral contraceptives for 10 years or longer had four times the risk of other women, according to one study.
LOW SOCIOECONOMIC STATUS increases the risk, in part because of reduced access to health care services.
FAMILY HISTORY, DES: If a member of your immediate family has cervical cancer, your risk is increased two- to three-fold. Women whose mothers were given DES (diethylstilbestrol), a hormone prescribed between 1940 and 1971 to prevent miscarriages also have a higher than average risk.
Once it becomes widely used, the vaccine will reduce many of the above risks. But neither vaccine protects against all causes of cervical cancer. Screening with the Pap test or HPV test is recommended once a year for all women starting about three years after they start having sexual intercourse but no later than age 21. After age 30, depending on risk factors and results of tests, some women can have screening every two or three years.
With immunization along with careful attention to screening tests, women now have a way to gain the upper hand on cervical cancer.
REFERENCES:
American Cancer Society, “Cancer reference information, detailed guide: cervical cancer,” August 24, 2006.
Donya C. Arias, “New vaccine for cervical cancer virus raises access questions: vaccine approved,” Nations Health, 2006;36(6), Medscape August 2, 2006.
Laurie Barclay, M.D., “HPV vaccine may prevent most cervical cancer, precancerous lesions,” Medscape Medical news, June 28, 2007.
Salynn Boyles, “Study shows Cervarix protects against virus that can cause cervical cancer,” WebMD Medical News, June 27, 2007.
“Cervical cancer,” MayoClinic.com, June 29, 2007.
“Globally, cervical cancer most often due to vaccine-susceptible HPV 16/18,” Reuters Health, August 24, 2007; International Journal of Cancer 2007; 121:621-632.
“HPV and cervical cancer: what women and girls should know,” WebMD Medical Reference, April 24, 2007.
“HPV testing supported as sole primary screening test for cervical cancer,” Reuters Health, April 14, 2006; International Journal of Cancer, 2006;119.
National Cancer Institute, “Cervical cancer (PDQ), last modified September 20, 2007.
Mack T. Ruffin IV, M.D., M.P.H., “Family physicians’ knowledge of risk factors for cervical cancer,” Journal of Womens Health 12(6):561-567, 2003.
Andrew L. Sussman, Ph.D., et al, “HPV and cervical cancer prevention counseling with younger adolescents: implications for primary care,” Annals of Family Medicine 2007;5(4):298-304.
“UK mothers back cervical cancer vaccine for kids,” Reuters Health, January 24, 2007
“Visual screening with acetic acid cuts cervical cancer mortality in poor countries,” Reuters Health, August 2, 2007; The Lancet 2007;370:365-366, 398-406.
