BOSTON, Feb 13, 2003 (United Press International via COMTEX) -- Scientists have discovered that using the patient's own tumor cells in a therapeutic vaccine helped boost the immune system to fight lung cancer, according to a new study released Thursday.

Researchers at Dana-Farber Cancer Institute in Boston found this prototype experimental vaccine proved effective in a handful of patients with advanced non-small cell lung cancer, an aggressive type of cancer that is the leading cause of cancer deaths in the United States.

"The reason we're using patient's own tumor cells, we think that maximizes chances for developing strong immune response to patient's own tumor," lead study author Dr. Glenn Dranoff, told United Press International.

In this clinical trial, 34 patients with metastatic lung cancer, meaning the cancer had spread elsewhere in the body, were given this vaccine. Although vaccines typically are administered to prevent an illness, therapeutic vaccines are developed with the hope of boosting the body's own immune system to fight the disease.

To create the vaccine, a portion of the patient's tumor is removed and a gene called granulocyte-macrophage colony-stimulating factor or GM-CSF protein is inserted into the tumor cells. GM-CSF works as a magnet for the immune system by attracting immune system cells to tumor cells.

The tumor cells then are radiated. A specially engineered virus is added to the vaccine to help direct it into the body. This technique originally was developed to combat melanoma, a lethal form of skin cancer, and results from those studies showed the vaccine triggered a long-lasting immune system response to the cancer.

The same proved true for the lung cancer patients in the study. Nine had to withdraw because their disease progressed too rapidly. Two patients remained disease-free three years after vaccination. Five patients had periods ranging from three months to 33 months where their cancers had stopped spreading. Eighteen patients had heightened levels of immune system cells after vaccination.

Tumor samples taken after vaccination also showed immune system cells had penetrated the tumors in three patients. Side effects were minor with the only complaint being irritation at the site of vaccine injection.

"The results are very preliminary, but they are encouraging," Dranoff said. "It's highly experimental."

This was only a Phase 1 clinical trial and the vaccine now has gone on to Phase 2 trials. Government requirements call for three intense phases of clinical testing before a treatment can be considered for approval for public use.

"Cancer vaccines are under very active study," Dranoff added. "Most work to date has focused on a smaller number of tumors, for example melanoma, and there has been much, much less attention to the more common types of cancer like lung cancer and that's one important contributions to this study."

Dr. Rowan Chlebowski, a medical oncologist at Harbor-University of California at Los Angeles Medical Center and Research Education Institute, told UPI the intriguing part of the study is its "novel approach" in using the patient's own cancer to fight itself.

Chlebowski said, however, the farther the cancer has spread, the more difficult it would be to treat using the body's own immune system.

"Immunological therapies depend on cell to cell interactions," he said, "(so) the numbers run against you when you have metastatic disease."

The findings also suggest, he added, that cancer treatments are becoming more customized to the individual patient. "The potential advantage to this is using the individual's own tumor cells," he noted.

This study is published in the February 15 issue of Journal of Clinical Oncology.

(Reported by Katrina Woznicki, UPI Science News, in Washington)

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