DNA Test for HPV, the Virus Associated with Cervical C., Receives FDA Approval
At least 93% of cancers and high-grade precancerous lesions of the cervix may be associated with infection with the human papillomavirus (HPV), a disease that is sexually transmitted. The U.S. Food and Drug Administration (FDA) recently approved the High-Risk Hybrid Capture II HPV, a new test used to detect the 13 types of HPV that are associated with cervical cancer. Currently, this new test is limited to use in women who have an abnormal or unclear Pap smear result (called ASCUS); however, the manufacturer is also seeking approval for use of the new test in conjunction with the Pap smear for primary cervical cancer screening.
Cancer of the cervix, the part of a woman’s reproductive system that connects the uterus (womb) to the vagina (birth canal), is considered to be one of the more preventable types of cancer. There are a number of known characteristics, or risk factors, that can increase a woman’s chance of developing cervical cancer. These include smoking, having a poor diet, being infected with HIV, and not receiving regular screening (testing and examination) for cervical cancer. The long-term use of oral contraceptives is suspected of slightly increasing the risk for cervical cancer, and studies are underway to make this determination. However, the most important risk factor for cervical cancer is HPV infection, a disease that is sexually transmitted. Women with certain other risk factors, such as having had sexual intercourse before age 16 years and/or having had many sexual partners, are at a higher risk for infection with HPV and thus development of cervical cancer. There are numerous types of HPV. Although it is still under study, many types of HPV are thought not to, or to only rarely, develop into cancer (called low-risk HPV). However, at least 13 types of HPV are known to be associated with cervical cancer (called high-risk HPV).
There are 2 main ways to help reduce one’s risk of developing cervical cancer. The first is to avoid the risk factors. Avoiding smoking; having a healthy diet; and avoiding HPV infection by delaying sexual activity and/or limiting one’s number of sexual partners help to reduce the chances of developing abnormal precancerous cells and thus cancer cells.
The second important step in reducing this risk is to see a doctor annually for examination and a Pap smear. The American Cancer Society recommends a yearly Pap smear for all women, starting at 18 years of age or when sexual activity begins, whichever comes first. Routine screening with a Pap smear is used to detect cancerous cells in the cervix early as well as to detect abnormal cells in the cervix before they become cancerous. A Pap smear consists of the removal of cells from the cervix and examination of these cells under a microscope. The cells are classified as 1 of 5 types: negative or within normal limits (normal); atypical squamous cells of undetermined significance (ASCUS); low-grade squamous intraepithelial lesions (abnormal); high-grade squamous intraepithelial lesions (abnormal); or carcinoma (cancer). A woman whose results are normal needs no treatment and simply continues to undergo an annual examination and Pap smear. For a woman whose results show cells that are clearly abnormal but not yet cancerous, more diagnostic procedures are done and, if needed, treatment is provided to prevent cancer from developing. However, for women whose results are categorized as “ASCUS”, the followup measures are less certain. The doctors cannot determine whether the cells are likely to progress into cancer or not. Often, women with ASCUS results are asked to repeat the Pap smear; some undergo treatment as though they have more clearly abnormal Pap smears, even though the treatment may not be needed.
Although the routine use of the Pap smear has resulted in a significant decline in deaths from cervical cancer, the results are not always accurate (false positives, false negatives) and are sometimes difficult to interpret, as noted. The newly approved High-Risk Hybrid Capture II HPV test may help determine whether treatment is needed for women whose Pap smear results are categorized as ASCUS. This new DNA-based test allows the identification of cancer-associated HPV present in the cervical cells, a function the Pap smear does not provide. Therefore, women with Pap smear results categorized as ASCUS can undergo further evaluation with the new HPV test to identify whether any cancer-associated HPV types are present. An ASCUS Pap smear and the detection of a high-risk HPV type would suggest the presence of high-risk precancerous cells, requiring further diagnostic testing and treatment if necessary. Alternatively, an ASCUS Pap smear and detection of a low-risk HPV type would suggest the presence of cells that are less likely to progress to cancer and can be managed less aggressively.
At this time, the High-Risk Hybrid Capture II HPV test is approved for use in women who have abnormal or unclear (ASCUS) Pap smear results. However, the manufacturer is seeking approval to use the High-Risk Hybrid Capture II HPV, in conjunction with the Pap smear, as part of primary routine screening for cervical cancer. (Digene Corporation Receives FDA Approval for High-Risk Hybrid Capture II HPV DNA Test, Digene Corporation, News release, www.digene.com, 2000)