Vaccine for cervical cancer shows dramatic results
An international clinical trial directed by Diane Harper of the Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center (DHMC) and Dartmouth Medical School has shown promising results for a vaccine against the most common causes of cervical cancer.
Writing in the lead article of the Nov. 13 issue of The Lancet, Harper and her fellow authors said the vaccine has the potential to greatly reduce deaths from cervical cancer, which is one of the leading causes of cancer mortality among women worldwide. The vaccine is targeted to immunize against two types of high-risk human papillomavirus, HPV-16 and HPV-18, which cause an estimated 70 percent of cervical cancer cases.
HPV is a commonly occurring infection, transmitted by skin-to-skin contact, most commonly through normal sexual interactions. Although most cases of HPV resolve themselves through natural immunity, a percentage of cases will progress to cervical cancer. Currently, an estimated 280,000 women die from cervical cancer each year, most of them in the developing world. Of the 500,000 cases of cervical cancer diagnosed annually, 70 percent are attributed to infection from HPV-16 and18. The five-year prevalence of cervical cancer worldwide – in other words, the number of women in any five-year period of time with cervical cancer – is 1.4 million.
Participants in the blind, randomized trial of 1,113 women from the United States, Canada and Brazil, received three doses of the experimental vaccine or a placebo over six months. At 27 months of follow-up, the vaccine showed an extremely high rate of efficacy. In those women who completed the protocol – receiving all three shots and participating in all scheduled testing and follow-up – the vaccine was 100 percent effective against persistent HPV16 and HPV 18 infections.
Significantly, the efficacy was only slightly reduced for those women who did not fully comply with the protocol – receiving only one or two of the three shots or not completing all scheduled follow-up appointments. In that group, the vaccine proved 95 percent effective against persistent HPV infection and 93 percent effective against cytologic abnormalities associated with HPV 16 and 18 and provided complete protection from cervical tissue changes due to HPV16 and 18.
Harper, a clinician who actively treats women in obstetrics and gynecology at DHMC, as well as a researcher, is internationally recognized for her pioneering work on HPV. The results of this study are “extremely exciting and encouraging,” Harper said. “We believe this shows enormous potential to eradicate the great majority of cervical cancers worldwide.”
Harper said that while other vaccines against HPV are currently being tested, this trial is notable because it is the first to target two viruses with one vaccine.
“Our trial results showed a high degree of safety, with no adverse effects to the participants, and highly significant and complete protection against persistent infection. This has enormous implications for women worldwide, and for our health system, which annually spends billions of dollars on cervical screening programs,” she said.
Recruitment for a larger, Phase III trial of the vaccine – the last step prior to licensing the drug for general use – is now underway at Norris Cotton Cancer Center and other sites. “We hope these results will encourage women to sign up for this trial,” Harper said. The Norris Cotton Cancer Center is the only Northeastern site other than Philadelphia participating in the large-scale trial, so women from throughout New England who meet the criteria and are interested are advised to enroll here. For more information on the trial, e-mail or call Lisa Matthews at 653-3692.
The vaccine discussed in The Lancet article and in the larger trial now underway is being developed and would ultimately be licensed by GlaxoSmithKline. Harper is an independent researcher who acted as primary investigator and is neither paid nor employed by GlaxoSmithKline.
Source: Story By DEBORAH KIMBELL, VOX Newspaper for Dartmouth Falculty and Staff