Enlisting the immune system in the fight against cancer

Doctors have overcome 30 years of false starts and found success with a new 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.

Researchers at a cancer conference in Orlando said Sunday that one such vaccine kept a common form of lymphoma from worsening for more than a year. That’s huge in this field, where progress is glacial and success with a new treatment is often measured in weeks or even days.

Experimental vaccines against three other cancers -- prostate, melanoma and neuroblastoma, an often fatal childhood tumor -- also gave positive results in late-stage testing in recent weeks.

Researchers at the annual meeting of the American Society of Clinical Oncology were cautious about the results so far. 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.

A big 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.

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 now held by Biovest International Inc. of Worcester, Mass., and some of his co-researchers have financial ties to the company.

Researchers gave 41 patients the shellfish protein and an immune booster; 76 others received those plus the vaccine. After nearly five years, the average time until the cancer worsened was 44 months in the vaccine group and 30 months in the others.