Cancer fighters look at immune therapies
June 1, 2009
ORLANDO, Fla. - First there was surgery, then chemotherapy, then radiation. Now, doctors have overcome 30 years of false starts and found success with a fourth way to fight cancer: using the body's natural defender, the immune system.
The approach is called a cancer vaccine, although it treats the disease rather than prevents it.
At a cancer conference yesterday, researchers said one such vaccine kept a common form of lymphoma from worsening for more than a year. That's huge in a field where progress is glacial and a new treatment's success is often measured in weeks or days.
Experimental vaccines against three other cancers - prostate, the deadly skin disease melanoma, and an often fatal childhood tumor called neuroblastoma - also produced positive results in late-stage testing in recent weeks after decades of struggles in the lab.
"I don't know what we did differently to make the breakthrough," said Dr. Len Lichtenfeld of the American Cancer Society.
It is too soon to declare victory. No one knows how long the benefits will last, whether people will need boosters to keep their disease in check, or whether vaccines will ever be a cure. Many vaccines must be custom-made for each patient. How practical will that be, and what will it cost?
Those are all good questions, but there are no answers yet, said Dr. Richard Schilsky, a University of Chicago cancer specialist who is president of the American Society of Clinical Oncology.
Several vaccine studies were reported during the weekend at the oncology group's annual meeting in Florida.
A problem has been getting the immune system to see cancer as a threat, said Dr. Patrick Hwu, melanoma chief at the University of Texas M.D. Anderson Cancer Center. Viruses like the flu or polio are easily spotted by the immune system because they look different from human cells.
"But cancer comes from our own cells. And so it's more like guerrilla warfare - the immune system has trouble distinguishing the normal cells from the cancer cells," he said.
To help it do that, many cancer vaccines take a substance from a cancer cell's surface and attach it to something the immune system already recognizes as foreign - in the lymphoma vaccine's case, a shellfish protein.
To make the attack as strong as possible, doctors add a substance to put the immune system on high alert.
Dr. Stephen Schuster of the University of Pennsylvania School of Medicine led a study testing BiovaxID, an experimental vaccine against follicular lymphoma developed by the National Cancer Institute. Rights to it are held by Biovest International Inc. of Worcester, Mass., and some of his coresearchers have financial ties to the company.
To be in the study, patients had to have achieved a remission for at least six months with standard chemotherapy. Remission often occurs with this type of lymphoma, but the disease usually comes back.
Researchers gave 41 patients the shellfish protein and an immune booster; 76 other patients were given those plus the vaccine. After nearly five years of follow-up, the average time until the cancer worsened was 44 months in the vaccine group and 30 months in the others.
Doctors unconnected with these experiments are cautiously optimistic.
"We've raised so many false hopes in the past," said Lichtenfeld of the Cancer Society. "What's different this time is we have the science reports to back up improvements."
