Experiment at Fred Hutch raises hopes in battling brain tumors

A gene-therapy experiment at Fred Hutchinson Cancer Research Center only involved a handful of brain-tumor patients, and on average, extended their lives by months, not years.

Even so, it was the first real progress in 30 years for patients with glioblastoma, the most common and most aggressive type of primary brain tumor the type that killed U.S. Sen. Edward Kennedy within 15 months of diagnosis.

I think this is actually one of those proof-of-concept milestones, said Dr. Stanton Gerson, director of the Case Comprehensive Cancer Center at Case Western Reserve University in Cleveland, who was not involved in the study. This is the very first clinical validation that all that science made sense.

The new approach, led by Dr. Hans-Peter Kiem and Dr. Jennifer Adair at Fred Hutch in Seattle, was published Friday in The Journal of Clinical Investigation.

It began with the usual therapy for such tumors powerful chemotherapy combined with a drug that disables a protein that makes some of these tumors particularly resistant to chemotherapy. More than half the patients with glioblastomas, including all seven patients enrolled in the study, have such a protein, Kiem said.

The protein-disabling drug, benzylguanine, is critically important because it allows chemotherapy to attack the tumor. But the drug also damages bone marrow, killing blood cells so people are left vulnerable to infection and bleeding, he said. For that reason, patients typically can receive only one or two cycles of chemotherapy.

The gene-therapy approach involved taking the patients stem cells and engineering them to become resistant to benzylguanine, so their blood cells werent damaged by the drug. When the stem cells were returned to the patients, their blood was protected but their tumors were left vulnerable to the chemotherapy.

Better protected against infection and bleeding, the seven patients in the study were able to receive more cycles of chemotherapy.

We can sensitize the tumor, while the blood cells are resistant, Kiem said. That is the trick.

Typical median survival for glioblastoma patients with the tumor-protecting protein is less than 13 months. The patients in this study, on average, survived 20 months, and all survived beyond one year. This is quite remarkable, he said.

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Experiment at Fred Hutch raises hopes in battling brain tumors