Viruses Stopped By Mercks Gardasil Cause Most Cervical Cancer
The two kinds of human papillomavirus, HPV16 and HPV18, together were found responsible for about 66 percent of the invasive cases of cervical cancer diagnosed in women in New Mexico, where the research was conducted. Both HPV16 and HPV18 are targeted by the vaccine approved for use in the U.S., Gardasil, as well as GlaxoSmithKlines Cervarix, which is still awaiting a decision by U.S. regulators.
The results, published in todays Journal of the National Cancer Institute, led the authors to question whether widespread use of the vaccine may eventually enable women to postpone testing for cervical cancer.
Waiting to screen “reduces the financial costs and helps support the burden of the cost of vaccination,” said Cosette Wheeler, lead author of the research and a professor at the University of New Mexico in Albuquerque, in a March 20 telephone interview. “It will be a long time until we have populations that have high enough coverage from vaccines to do that.
Each year about 10,800 new cases of cervical cancer caused by HPV16, HPV18 and other types of HPV are diagnosed in the U.S., according to the U.S. Centers for Disease Control and Prevention.
Checking for Cancer
Screening tests for cervical cancer are recommended now for women at age 21 or three years after they start sexual activity. Most doctors start screening women annually at 18 or younger, according to Lauri Markowitz at the CDC, a U.S. health agency in Atlanta.
The study is the largest in the U.S. to examine which types of HPV are responsible for most cervical cancers, the researchers said. The new work was funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute. Wheeler reported she has received research support from Merck, of Whitehouse Station, New Jersey, and GlaxoSmithKline, of London.
The analysis was done by looking at tissue samples preserved from more than 2,000 women in New Mexico who were diagnosed with either early cervical cancer or an invasive form of the disease in the 1980s and 1990s before vaccination was available.
HPV Types
They found that HPV16 was responsible for more than 56 percent of both early cancer, and for 53 percent of the cases that were invasive, when cancer had penetrated deep into the cervix and possibly beyond. HPV18 was responsible for about 13 percent of the malignancies that were invasive.
Those who developed invasive cervical cancer caused by HPV16 or HPV18 tended to be younger than women who had the malignancy caused by other types of HPV. The average age at diagnosis of HPV16 invasive cancer was 48.1 years, while for HPV18 it was 45.9 years. For other HPV cancers, the average age at diagnosis was 52.3 years, the study found.
Screening Debated
“Vaccine coverage will likely increase in the United States, but it may be years before a highly vaccinated cohort reaches cervical cancer screening age,” Markowitz said in an editorial that accompanied the study.
If some groups of women dont get vaccinated as soon as they reach the appropriate age, that may complicate any future changes in recommendations for cervical cancer screening, Markowitz wrote.
Wheeler said she thought vaccination should ultimately allow women to start being screened for cervical cancer later — as long as a large enough group of people are receiving the vaccine. Screening alone has already reduced the incidences of HPV16, the most common type, over 20 years, she said.
Studies need to examine the effect that vaccinations have on reducing cervical cancer rates, independent of screenings, Wheeler said.
“Many more years of data are required to know what we will be able to do to integrate screening with vaccination,” she said.
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