Therapeutic cancer vaccines show promise

It's a deceptively simple idea: What if doctors could recruit the body's own immune system to fight cancer? The complexities of the immune system have kept this from becoming reality, until now. Three cancer vaccines -- for prostate cancer, melanoma and lymphoma -- have achieved positive results in so-called Phase 3 clinical trials -- the kind of studies that the Food and Drug Administration requires for a medicine to gain approval.

At the annual meeting of the American Society of Clinical Oncology held May 29 to June 2, researchers reported that a vaccine against follicular lymphoma, called BiovaxID, delayed remission after chemotherapy by more than one year, on average.

At the same meeting, other researchers said that a melanoma vaccine caused tumors to shrink in twice as many patients as those receiving a standard FDA-approved therapy.

And at the annual meeting of the American Urological Assn. in April, researchers reported that the vaccine Provenge extended the lives of men with metastatic prostate cancer by four months, on average.

Doctors are cautiously optimistic about the news. "Researchers have been working very hard to get some positive results," says Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society in Atlanta. "These three trials do suggest that vaccines will be used in the actual treatment of patients in the not too distant future."

But even with these tentative successes, a big question remains open: Will vaccines ever become more than small players in the medical treatment of cancer -- a group of diseases that presently kills some 560,000 Americans each year?

Only two cancer vaccines currently have FDA approval and both are strictly preventive, targeting viruses that can lead to cancer. Most U.S. children are vaccinated against hepatitis B, a virus that can cause liver disease and cancer. A vaccine for genital human papillomavirus (HPV), which can cause genital warts and cervical cancer, is now recommended for adolescent girls.

The new medicines -- called therapeutic cancer vaccines -- act differently. They are not preventive in the traditional concept of vaccines. Rather, patients already afflicted with cancer are vaccinated in the hope that the shots will tell their immune systems how better to fight growing tumors. And because the immune system has a long memory, it's hoped that this immune boost might also ward off cancer recurrences.