Major Cancer Breakthrough?

(CBS)  Cervical cancer is a leading cause of cancer related death among women worldwide, killing more than 250,000 every year. But as CBS News Correspondent Elizabeth Kaledin reports, scientists say this pervasive cancer may have met its match in the form of a vaccine.

The vaccine targets a specific strain of the human papilloma virus or HPV, a sexually transmitted disease known to cause 50 percent of cervical cancers. Early results published in tomorrow's New England Journal of Medicine will show it works.

According to Dr. Katherine Van Kessel of the University of Washington Medical School, "In the first one and a half years, it was 100 percent effective."

768 women aged 16 to 23 got the vaccine and every single one developed immunity to HPV, and as a result, no one got the virus or any early signs of cancer. Of 765 who took dummy injections, 41 came down with persistent infections, and nine developed precancerous tissue.

Inoculated women built up almost 60 times the concentration of virus-fighting antibodies seen in naturally infected women. Some researchers had suspected that the mucous membrane on the cervix would pose a barrier to such antibodies.

To gynecologic surgeons like Dr. Carol Brown, a gynecologic oncologist at Memorial Sloan Kettering Cancer Center, the news is a breakthrough discovery.

"It's really the first time that a vaccine has been shown to prevent directly a pre-cancerous condition and indirectly a cancerous condition," Brown tells Kaledin.

Researchers foresee this vaccine becoming a valuable weapon in the public health arsenal and one day becoming part of every woman's routine health care.

"You would potentially look at vaccinating young girls prior to their sexual debut, girls who are age 10 to 12," says Van Kessel.

Vaccines work by teaching the body's immune defenses to recognize invading viruses and bacteria. Most types of cancer, by contrast, are blamed largely on genetic mutations and environmental factors. However, virtually all cases of cervical cancer are caused by a sexually transmitted virus — the human papilloma virus.

A vaccine for cervical cancer is urgently being sought because the disease strikes about 450,000 women worldwide each year, killing about half. It is the leading cancer killer of women in the developing world. In the United States, where Pap tests are widely used for screening, it develops in about 15,000 women annually and kills about a third.

Although this particular vaccine targets a virus and not the cancer itself, doctors believe its success has broader implications. Perhaps a variety of cancers could one day go the way of smallpox and polio, wiped out by vaccines that bolster the body's immune system.

A vaccine is already used to combat the hepatitis B virus, a sexually transmitted agent blamed for some cases of liver cancer.

"In general, vaccines are being studied in melanoma. They are being studied in ovarian cancer," explains Brown.

Laura Koutsky, a disease specialist at the University of Washington, also cautioned: "We really only know about the short-term duration of the antibodies. Whether the antibodies persist for five years or more is not known at this point."

Dr. Douglas Lowy, a National Cancer Institute researcher, agreed that patients must be tested over longer times. But he and others agreed that a vaccine — probably one targeted at multiple viral strains encompassing the vast share of cases — might reach market fairly quickly.

Such a vaccine could also stop other harm done by the virus, including genital warts in both men and women and rare forms of penile, anal, vaginal and oral cancer. Researchers said the vaccine might also be taken by men to keep them from infecting their female partners.

In addition, doctors say if the vaccine takes off on a large scale, it could one day cut back on the need for pap tests -- the current screening procedure for cervical cancer.

But for every hope raised by this study's success, there are many unanswered questions. Researchers still don't know how long the immunity lasts or if women will need booster shots. They don't know if vaccine can work against the many different strains of HPV that exist and, perhaps most important, when the FDA will approve such a vaccine for mass consumption. The thinking, however, is it's still several years away.