Vaccine prevents cervical cancer

Large study finds near-100% success against HPV cause

October 07, 2005|By JONATHAN BOR | JONATHAN BOR,SUN REPORTER

In what is hailed as a public health breakthrough, a pharmaceutical company reported yesterday that an injected vaccine can prevent the vast majority of cervical cancer cases.

The vaccine, which Merck & Co. will soon submit to the Food and Drug Administration for approval, works by arming the immune system against sexually transmitted viruses that trigger the cancer.

Known as Gardasil, it would be only the second vaccine to prevent cancer. The other guards against hepatitis B infections, a leading cause of liver cancer in Asia but not the United States.

In a trial that involved 12,000 sexually active women in the United States and 12 other countries, the company reported that Gardasil was 100 percent effective in preventing cancers and pre-cancerous growths caused by two types of the so-called human papillomavirus (HPV). Together, those types account for about 70 percent of cervical cancers worldwide, experts say.

The company followed its test subjects for an average of two years, and it plans to continue monitoring the women for years to see whether their immunity remains strong.

"I think it's tremendously big - a major advance in terms of protection against papillomavirus and disease," said Dr. Raphael P. Viscidi, an HPV researcher at the Johns Hopkins School of Medicine who was not involved in the study.

"I think it will completely change the clinical practice with regard to HPV infections," he said. "The generation of women who have access to this vaccine will probably have a vanishingly small risk for cervical cancer."

As the cancer risk falls, many women would be spared costly and bothersome biopsies, surgeries and medical treatments, he said.

The vaccine is also designed to prevent two other types of HPV associated with genital warts. These growths, which are at times painful and disfiguring, do not normally turn cancerous. The company plans to report the vaccine's effectiveness against genital warts later this year.

In the coming weeks, Merck officials said, they plan to ask the FDA for permission to market the vaccine commercially.

Cervical cancer is not very common in the United States, with 10,000 new cases diagnosed annually and 3,000 deaths attributed to it. Deaths have dropped off drastically because of routine Pap smears, a test that detects precancerous cells that can be surgically removed.

But worldwide, it is the second-leading cause of cancer mortality in women - with deaths highest in developing nations where Pap smears are not routine. About 300,000 women die annually of the disease.

Overseas market

A company official said the vaccine could find a large market overseas. "The developing world is very important," said Dr. Eliav Barr, senior director of clinical research at Merck Research Laboratories. "There's no Pap test there, and women are dying at a very young age from cervical cancer."

Though cervical cancer in the United States kills far fewer women than breast, uterine or ovarian cancer, the human papillomavirus that triggers it is common.

Most sexually active men and women become infected with HPV at some time in their lives. Though the immune system clears most infections, others will persist and spur genital warts or abnormal cells that can turn cancerous.

In the vaccine trial, sexually active women 16 to 26 years old were randomly assigned to receive three vaccine injections or an equal number of dummy shots over a six-month period.

None who received the active vaccine developed cervical cancer or pre-cancers associated with HPV types 16 and 18 - the ones the vaccine is designed to fight.

In contrast, 21 women who received placebo injections developed the dangerous conditions.

"To have 100 percent efficacy is something that you have very rarely," Barr told the Associated Press. "We're breaking out the champagne."

The results were welcome news for Merck, which has been rocked by the removal of its blockbuster painkiller, Vioxx, from the market after studies showed it can put users at risk for cardiovascular disease.

The new vaccine is designed to prevent infections and the resulting cancers, but not to cure the conditions once they have occurred.

Other kinds, causes

Dr. Douglas Lowy, a researcher at the National Cancer Institute, cautioned that women cannot assume that the vaccine eliminates all risk of cervical cancer. That's because the vaccine does not prevent other HPV types that account for about 30 percent of cervical cancers. For this reason, he said, even vaccinated women will need to be screened.

Also, Lowy said, no one yet knows how long immunity lasts once a person has been vaccinated. To answer this question, Merck plans to continue monitoring volunteers for many years and will recommend boosters if immunity appears to wane.

Given those cautions, Lowy said, the results are extremely encouraging.

"To those of us who are close to the field, we were expecting the results to be good, but I wouldn't say we were expecting them to be as unequivocal as they appear to be," Lowy said.

Dr. Sandra Brooks, director of gynecologic oncology at the University of Maryland School of Medicine, said the results were "a major breakthrough."

"The issue is who is going to get vaccinated and when," Brooks said.

Because the vaccine prevents an infection that is widespread among sexually active people, those most likely to benefit are teenagers.

"In order for it to be widely applicable, you'd want to choose a group of people before they become sexually active," she said. "I'm not sure the American public is ready for that."

Also, there remains a question of whether boys as well as girls should be vaccinated. Though it prevents a women's cancer, the vaccine could reduce transmission more effectively if given to both genders.

Merck shares fell 6 cents yesterday to close at $26.83 on the New York Stock Exchange.

jonathan.bor@baltsun.com

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