(WOMENSENEWS)–Cancer screenings usually search for abnormal cells that have multiplied to form a small tumor. The cancer starts off so tiny that doctors are unable to catch it until it has progressed to the point of being big enough to be seen during a mammogram or x-ray–when treatment is much more difficult.
But the beauty of cervical cancer screening, traditionally the Pap test, is that itidentifies abnormalities before cancer everdevelops. Doctors and women may now have a chance to prevent the disease before it starts.
New procedures might boost the odds of identifying women at high risk of developing the disease, announced experts who gathered at a media roundtable sponsored by the Society for Women’s Health Research in Washington, D.C., this week.
Experts from leading health organizations like the American College of Obstetricians and Gynecologists and the American Cancer Society expressed consensus that Human Papillomavirus (HPV), a widespread infection, causes virtually all cases of cervical cancer. They also highlighted revised cervical cancer screening guidelines with changes in screening frequency and new testing techniques.
Cervical cancer now ranks 13th in cancer deaths among U.S. women, although it is still the third most common cause of cancer-deaths in women worldwide. Countries in North America and Western Europe that have established routine cervical screening programs have significantly reduced deaths from the disease in the last 50 years. Still, 13,000 U.S. women develop cervical cancer each year, the majority of whom didn’t have the benefit of regular cervical screening. About 4,400 die annually of the disease in the U.S.
"Cervical cancer is one of the only cancers identified that really has a single cause–HPV infection," says Dr. Diane Solomon. "But it’s important to recognize that HPV infections are very, very common, and only a small percentage of women infected with HPV are actually at risk of developing the cancer," adds Solomon, a senior investigator for the National Cancer Institute at the National Institutes of Health in Rockville, Md.
In fact, it’s estimated that 75 percent of people who have been sexually active will acquire HPV at some point in their lives. HPV is the most common sexually transmitted virus in the U.S., with as many as 5 million women newly infected each year. Of the 100 strains of HPV, most cause no symptoms and pose no harm. But a handful of kinds, called "high risk" types, are now known to cause cervical cancer.
"Most women infected with HPV will never know they have had an infection, since the majority of infections, even those with high-risk types, will be recognized by the immune system and cleared before any symptoms are detected," says Dr. Patti Gravitt, assistant professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Md. "In rare cases, however, a high risk virus persists for more than one to two years, often forming a lesion on the cervix. Over a period of many years, an untreated precancerous lesion may progress to cancer," she says.
"Cervical cancer is not something that develops overnight, over weeks, or over months, but over 10-20 years," says Solomon.
New Techniques, Better Screening
Both the American Cancer Society and the American College of Obstetricians and Gynecologists have released revised screening guidelines in the past year based on new techniques that will hopefully make effective screening for cervical cancer easier and less frequent.
A woman’s first screening should take place either three years after becoming sexually active or at age 21, whichever comes first. Women under age 30 are more likely than older women to acquire HPV infections, and are generally advised to undergo annual Pap screenings. Chances of acquiring the virus increase with number of potential exposures to HPV. That can mean multiple partners or one partner who has had multiple partners.
Two new methods increase the accuracy of the traditional Pap test, which takes a sampling of cells from the cervix and checks for abnormalities. A new liquid-based test immerses the cell sample into liquid rather than onto a laboratory slide, garnering more sensitive results. There are two liquid-based tests currently approved by the FDA.
In addition, a new DNA HPV test examines cells for genetic traces of the high-risk HPV types. This test, used in conjunction with the standard Pap test, is approved as a primary screening method for women age 30 or over, who are usually at less risk of acquiring HPV. The FDA has approved one type of DNA HPV test to date, put out by Digene Corporation.
"If both the Pap test and HPV test are negative, a woman has 99 percent reassurance that there’s no serious lesion there," says Solomon. She can return for her next test in three years. Increasing time between screenings could save women and their health insurance providers unnecessary, expensive testing and treatments.
A few categories of women shouldn’t cut back on the frequency of their testing: women who are living with HIV, who are immunosuppressed (such as transplant patients) or who are what are called DES daughters, that is, they were exposed to diethylstilbestrol in utero. The synthetic form of estrogen was given to pregnant women in the 1950s and 1960s and was later linked to cancer and other health problems.
Many Disadvantaged Women Not Being Screened
Educating women about the importance of HPV testing is complicated by the stigma associated with sexually transmitted disease. Questions about the date or source of acquisition are unanswered by the test. The virus can persist for years before it’s detected. Being diagnosed with a sexually transmitted infection, especially one that is associated with cancer, can be frightening and anxiety provoking.
About 80 percent of U.S. women have received a Pap test in the past three years. But rural women, minorities, older women who have never had screening or those who are of low economic status are especially likely to go unscreened, even if they visit their doctor.
The majority of women who develop and die of cervical cancer are those who are inadequately screened. At present, the best way to further reduce cases is moving women who are not screened regularly into testing.
"We need to educate providers, especially if they see older, minority, or low income women, to ask whether they’ve been screened," says Solomon.
If cervical cancer is caught early, it can often successfully be treated with a combination of surgery, radiation and chemotherapy.
There is promising research being conducted on an HPV vaccine. A November 2002 article published in The New England Journal of Medicine reported that a vaccine for the most common type of high-risk HPV, type 16, was effective in protecting women from acquiring the virus for about 18 months.
"Such a vaccine could make a big difference in countries where screening is not feasible or hasn’t worked and where cervical cancer is still common," says Gravitt. "A long-acting vaccine for a handful of the most common cancer-causing HPV types could potentially eliminate more than three quarters of cervical cancer cases worldwide."
Kathleen Nelson is a journalist who writes about health, science and medicine.
For more information:
American Cancer Society–Learn About Cancer:
Association of Reproductive Health Professionals:
Society for Women’s Health Research: