The vast majority of women worldwide who develop cervical cancer acquire it from sexually transmitted viruses, according to researchers from the Johns Hopkins School of Hygiene and Public Health.
It is now clear that cervical cancer should be fought as an infectious disease, scientists said, perhaps with a vaccine that would enable the body to hold the virus at bay before it has a chance to trigger cancer. The scientists, who examined tumors from 22 countries, found viral evidence in 93 percent of the cancers.
“This establishes that a sexually transmitted agent is responsible for one of the most important cancers in women,” said Dr. M. Michele Manos, a visiting scholar at Hopkins and one of the study’s chief investigators.
Cervical cancer is the second most common cancer in women worldwide and, by far, the most common and fatal in developing nations. There are about a half-million new cases each year, 80 percent of them in Third World nations.
A broad family of viruses - the human papillomaviruses (HPV) - has long been implicated as a major risk factor for cervical cancer. The viruses may be the most common sexually-transmitted agents in the world, although only a small percentage of infected women develop cancer.
The Hopkins study, appearing in today’s Journal of the National Cancer Institute, is the first to show that the viruses are the leading cause of cervical cancers on a worldwide basis.
The study was directed by Manos and Dr. F. Xavier Bosch of the World Health Organization, who were part of an extensive multinational team.
Efforts to develop a vaccine are under way, but are far from complete. Any globally effective vaccine would have to attack not just one virus - but the many that constitute the HPV family.
In the United States, a diagnostic test known as the Pap smear has caused the incidence of cervical cancer to drop by as much as 75 percent over the past four decades.
The Hopkins study found that more than 20 different types of human papillomavirus were associated with cervical cancers, although one appeared in half of the specimens. None of the viruses cause noticeable symptoms until they trigger the development of cancerous lesions, at which point the woman can experience bleeding.