As testing for high-risk types of the human papillomavirus (HPV) emerges as the gold standard in cervical cancer prevention, scientists are already researching how to determine even more precisely who is most likely to develop the disease and thus are in need of more immediate intervention.
Speaking at the EUROGIN (European Research Organization on Genital Infection and Neoplasia) conference THIS WEEK, experts presented data suggesting that the most effective strategy would be to introduce a second test to determine if women who test positive for high-risk HPV have one of three types of the virus that are associated with the highest mortality from cervical cancer: 16, 18 and 45.
About 30 HPV types are spread through genital contact, and about 18 of these can potentially cause cervical cancer. Each is "named" with a number, in the order of their discovery. Much attention has been paid to types 16 and 18, which account for 70 percent of all cervical cancers and against which the new HPV vaccines protect. However, experts say that medical evidence shows that type 45 should be a priority concern as well.
"Most of the focus has been on HPV types 16 and 18, because they are the most prevalent carcinogenic HPV types and are targeted by the new HPV vaccines," comments Attila Lorincz, PhD, one of the originators of the HPV test and Professor at Barts and The London School of Medicine. "However, type 45 also is highly associated with risk, particularly for adenocarcinoma, a very aggressive type of cervical cancer with a mortality rate of 52% after five years -- twice the rate of squamous-cell cancers. The incidence of invasive cervical adenocarcinoma, which used to account for 10-15 percent of all cervical cancers, has been steadily increasing -- in part because it develops inside the cervical canal and thus is difficult to detect early using a Pap smear."
Currently, there is one HPV test, developed by QIAGEN (Nasdaq: QGEN; Frankfurt, Prime Standard: QIA) and marketed as the digene HPV Test, which is approved by the U.S. Food and Drug Administration and is CE-marked in Europe. When used for screening, it is given to women over the age of 30 along with a Pap test, which can find abnormal cells but cannot detect HPV directly. And now, QIAGEN is developing two types of follow-up tests that will identify specifically which types of the virus are carried by HPV-positive women. At EUROGIN this week, QIAGEN scientists are presenting the results of research showing the accuracy of the company's digene HPV Genotyping PS Test, which specifically identifies the presence of types 16, 18 and 45. This assay is based on the technology used in QIAGEN's front-line HPV screening test, hybrid capture 2 (hc2) -- currently the gold standard in the field. In addition, data are being presented for a second QIAGEN assay, the digene HPV Genotyping RH Test, which identifies 18 types of potentially carcinogenic HPV. Prior to receiving CE marking in Europe, the genotyping tests will be made available for research use by laboratories and physicians exploring their potential clinical benefits. First to be available will be the digene HPV Genotyping RH Test, which is expected to be launched by the end of this year.
Currently, women who screen positive for high-risk HPV, but have normal Paps, are brought back for re-testing 12 months later, since it is only persistent infections that cause cancer. However, Dr. Lorincz explains that genotyping would allow women with HPV 16, 18 or 45 -- who are at highest risk of cervical cancer -- to be immediately examined further for the presence of pre-cancerous or cancerous cells.