HPV Test Effective for Women with Abnormal Pap Smears, Cervical Cancer Vaccine in Development
Some promising developments in cervical cancer research may help to further reduce the number of deaths from the disease. Researchers from the National Cancer Institute (NCI) are currently developing a vaccine that targets a specific strain of the human papillomavirus (HPV), a sexually transmitted disease that may increase the risk for cervical cancer. The vaccine was successful in animal trials, and in a small study with humans, most patients developed 40 times more antibodies against the HPV strain after receiving the vaccination. Further testing of the vaccine will include thousands of Costa Rican women. In the meantime, NCI researchers have found that HPV testing is effective for determining whether women with abnormal Pap smear results have pre-cancerous cells or cancer of the cervix and should be referred for further testing and/or biopsy. HPV testing can easily be performed by analyzing cervical cells in a pathology laboratory.
There are over 80 different strains of HPV, affecting more than 40 million Americans. While the majority of HPV strains do not pose health risks, a few strains increase the risk for cervical cancer (such as HPV-16, HPV-18, HPV-31, and HPV-45). Annual Pap smears help screen women for cervical cancer and have contributed to 75% decrease in cervical cancer deaths in the U.S since the mid-1950s.
Approximately 50 million Pap smears are performed each year in the U.S., and 2 million of the tests produce unclear results (a result called ASCUS). However, physicians are not able to determine whether those abnormal results are harmless or signal pre-cancerous conditions. Up until now, follow-up has typically consisted of either colposcopy (endoscopic viewing the cervix with magnification) with or without biopsy or repeat Pap smears. The majority of women who undergo follow-up do not have pre-cancer or cancer and do not need these procedures.
Now, in a study of 3488 women with unclear Pap results, lead researcher Diane Solomon, MD of the NCI and her colleagues have found that performing HPV testing on these women helped identify nearly all patients (96.3%) that needed treatment. HPV testing was also 99.5% successful in identifying women whose unclear Pap results were no cause for concerning, saving almost half of the women in the study from having to undergo unnecessary biopsies. Similar to a Pap smear, HPV testing involves collecting a sample of cervical cells from the patient. HPV testing may be performed at the same time as a Pap smear or subsequently (i.e., before a colposcopy). The cells are then analyzed in a pathology laboratory to determine whether the woman carries any strains of the HPV virus.
"These results indicate that HPV testing is a viable option from women and their doctors to consider when deciding what to do about ASCUS [unclear Pap results]," said Dr. Solomon, in an NCI press release.
While these results show HPV testing to be highly accurate, physicians say the test should not replace the Pap smear, which is a very effective screening tool for cervical cancer. Since 40 million Americans have HPV and most strains are harmless, testing for HPV is not beneficial unless Pap smears produce unclear results. Research also shows that the majority of women who are diagnosed with cervical cancer did not receive annual Pap smears to screen for the cancer.
The Digene Corporationâ€™s Capture HPV test has been approved by the U.S. Food and Drug Administration (FDA) since 1999 and costs approximately $50. Around 15% of women with unclear Pap results currently receive HPV testing. The recent NCI study results will be discussed at two upcoming conferences and may change guidelines for how women with unclear Pap results are evaluated.
Early Vaccine Research Shows Promise
In another study also published in the Journal of the National Cancer Institute, Douglas Lowy, MD and his colleagues reported early results of a vaccine that targets a specific strain of HPV (HPV-16) associated with cervical cancer. While the vaccine is still in development, animal studies have shown that the vaccine offers protection against HPV-16.
In 72 healthy people, the vaccine was well tolerated and significantly increased immune response to HPV-16. The researchers plan to continue testing the vaccine in a large group of women in Costa Rica, where cervical cancer incidence is high. A vaccine would especially benefit women in developing countries who cannot afford the $25 annual cost of Pap smears.
It is estimated that 400,000 women develop cervical cancer each year, including nearly 13,000 Americans. Deaths from cervical cancer have declined in the U.S. as more women now receive annual Pap smears. The American Cancer Society estimates that approximately 4,600 Americans die from cervical cancer each year. When detected early, the chances for successful treatment and survival are high. The 5-year survival rate for early invasive cervical cancer is approximately 91%. The overall 5-year survival rate for all stages of cervical cancer is around 70%, and for pre-invasive cervical cancer, the 5-year survival rate is nearly 100%.
The American Cancer Society recommends that all women begin receiving yearly Pap smears and pelvic examinations at age 18 or when they become sexually active, whichever occurs earlier. Some physicians will not perform a Pap smear each year if a woman has had three negative Pap smears in the course of three years. However, a yearly pelvic exam should be continued even if Pap smears are not given each year.
Regular or more frequent Pap smears may be performed on women who have had hysterectomies (surgery to remove the uterus, including the cervix), especially if the hysterectomy was performed because pre-cancerous or cancerous cells were found in the cervix. In women who have had hysterectomies, the tissues of the vagina are analyzed for changes that may indicate cancer.
In addition, women who have a weakened immune system (from AIDS, chemotherapy or drug treatments, or organ transplants) are considered at higher risk for cervical cancer and may require Pap smears more frequently than once a year.
Additional Resources and References
- The February 20, 2001 National Cancer Institute (NCI) press release, "HPV Testing Shows Which Pap Abnormalities Need Attention," is available at http://rex.nci.nih.gov/massmedia/pressreleases/altsrelease.html
- The study, "Comparison of Three Management Strategies for Patients with Atypical Squamous Cells of Undetermined Significance: Baseline Results From a Randomized Trial," is published in the February 21, 2001 issue of the Journal of the National Cancer Institute (Vol. 93, No. 4, 293-299). An abstract of the study is available at http://jnci.oupjournals.org/cgi/content/abstract/93/4/293
- The study, "Safety and Immunogenicity Trial in Adult Volunteers of a Human Papillomavirus 16 L1 Virus-Like Particle Vaccine," is published in the February 21, 2001 issue of the Journal of the National Cancer Institute. An abstract of the study is available at http://jnci.oupjournals.org/cgi/content/abstract/93/4/284
- The February 20, 2001 MSNBC.com report, Combating Cervical Cancer: Experimental Vaccine Virus Test Could Save Womenâ€™s Live," is available at http://www.msnbc.com/news/533584.asp
- To learn more about HPV testing, please visit the Digene Corporation website at http://www.digene.com/
- To learn more about Pap smear and cervical cancer, please visit http://www.imaginis.com/womenshealth/pap_smear.asp