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Vaccine targets killer cancer
Researchers believe a new, one-shot treatment will eradicate viruses that cause cervical cancers
More than 80 per cent of cervical cancers could be eradicated in the near future by a long-lasting vaccine that destroys the main viruses causing the disease, the lead author of a new study says.
The vaccine, which would be given to both girls and boys at puberty, has been shown to be 100 per cent effective in killing off four papillomavirus types that are responsible for the vast majority of cervical cancers, said Dr. Diane Harper, of New Hampshire's Dartmouth Medical School.
The disease kills roughly about 500,000 women a year worldwide and is second only to breast cancer as the leading cause of cancer deaths in females.
About 1,400 cervical cancer cases are diagnosed each year in Canada and about 400 women die of the disease.
"This is huge, this is really huge," said Harper, whose study will be published in today's online issue of the British medical journal Lancet.
"We're hoping that by the time I die ... there are one or two cases of cervical cancer (a year) and by the time my kids die, cervical cancer will go the way of smallpox."
Harper's paper, a follow to a 2004 study that showed the vaccine was effective in fighting the HPV 16 and HPV 18 viruses, suggests that one administration of the vaccine might last a lifetime.
The vaccine would be given to males and females in their teens since the HPV viruses can be passed from men and women during intercourse.
Health Canada notes that women are at increased risk of cervical cancer if they are sexually active or if they have many sexual partners.
Sexual activity at a young age can heighten the risk because during puberty cervical tissues are changing so rapidly and the area might be more vulnerable.
The virus can live on the outer cervical tissue for up to three years before migrating into lower cell layers, where it can reproduce, and cancer sets in.
"We're hoping there may be (only) one booster shot needed in a lifetime or maybe no booster shot needed in a lifetime," said Harper, who saw no increased viral loads in any of the 800 women she tested four and a half years after they were inoculated.
The vaccine's longevity is important, Harper said, because HPV viruses often work silently for a decade or more in the cervical area before the onset of cancer.
As well, a significant majority of cervical cancer deaths occur in poorer Latin American and Southeast Asian countries, where access to medical services is scarce and follow-up vaccines may be problematic.
Harper said the vaccine has also been shown to fight off two other cancer-causing viruses — HPV 45 and HPV 31.
But she said the vaccine does not herald an end to Pap tests, in which sample cells are taken from the cervix to detect abnormal changes that may arise from cancer or before cancer develops.
"The reason is that this (vaccine) covers (the target viruses) at 100 per cent efficacy," said Harper.
"But that's still only four of the 15 types that cause cervical cancer.
"That makes it really important for women to still get their Pap tests."
Harper is conducting a pair of clinical cervical vaccine trials at Dartmouth run by pharmaceutical companies GlaxoSmithKline and Merck.
She said she is not being paid by either company.
Dr. Donna Stewart, chair of women's health at the University of Toronto's University Health Network, said Harper's is one of several studies, published or in the works, showing immense promise from cervical cancer vaccines.
She said a Seattle study published last month produced similar results.
"But this is wonderful news," Stewart said.
"I think that the combined studies going on around the world right now ... are extremely positive and exciting."
An increasing number of studies indicate that a number of cancers are caused by viral infections.
