A melanoma vaccine under study has lengthened remissions among patients with a certain kind of "genetic fingerprint," or HLA type, said researchers in the Journal of Clinical Oncology (Vol. 20, No. 8: 2058-2066).

The HLA (human leukocyte antigen) proteins involved are found on the surface of cells. They are used in a variety of ways, such as matching organ donors with organ recipients so the body doesn't reject a transplanted organ, such as a heart or liver.

"We found patients responded much better to the vaccine if they had these pre-defined HLA types," said Vernon K. Sondak, MD, professor of surgery at the University of Michigan Comprehensive Cancer Center, and chair of the southwest oncology group melanoma committee.

Cancer vaccines are being developed to both fight and prevent several kinds of cancer, including melanoma.

Vaccines work by exposing the patient's immune system to proteins from the invader to be attacked, such as a virus, bacterium, or cancer cell. Certain cells in a patient's immune system recognize the injected protein as being "foreign" and signal other immune system elements to attack and destroy the injected proteins.

The vaccination leaves some immune system cells with the ability to recognize those foreign proteins. If the cancer returns it can be attacked and perhaps destroyed by the immune system.

Some cancer vaccines are made from the patient's own tumor cells, so they have the exact genetic fingerprint as the patient. Those are called autologous ("from oneself") vaccines.

But vaccines of the kind in Sondak's trial, called allogeneic ("from another"), are made from cancer cell proteins obtained from other patients, so they may contain material with different genetic fingerprints than the patient.

In 1992, Sondak and others began testing a well-known melanoma vaccine made from two different melanoma patients' tumors. Earlier, the vaccine had produced complete remissions in some patients with advanced cancer but not in others, and no one was certain why most patients didn't benefit.

At this time there is no accepted treatment after surgery to lower such patient's chances of a recurrence.

All of the patients in Sondak's trial had intermediate-thickness melanoma tumors removed earlier, and they showed no signs of melanoma spread to the lymph nodes.

When all 600 patients were lumped together, the 300 getting the vaccine didn't go significantly longer without relapse than the 300 not given the vaccine.

But midway through the study, Sondak revised the design of the trial. He began testing the participants' blood for HLA type, to see if patients might do better if their HLA types were the same as those who had done better in the earlier trial with advanced melanomas. The new research suggested they might.

They found that in patients who had two or more of the five HLA markers identified in the earlier trial as marking those with the best responses to the vaccine, 83% went five years or more without relapse, compared to only 59% of those not on the vaccine.

"This is a promising new development that holds great potential for the development of vaccines that can be individualized to maximize the benefit for each individual's personal genetic makeup," said Martin Weinstock, MD, PhD, director of dermatology at Brown University and chair of the ACS skin cancer advisory group.

Melanoma vaccines are currently available in the US only through clinical trials. Weinstock said such vaccines have been in development for many years but that "success with the vaccines against the disease in humans has been hard to come by."

"If these results are confirmed by other studies, it's likely we will see this approach — and more success — become the norm with these kinds of vaccines," added Weinstock.