Scientists at the Johns Hopkins Oncology Center have shown for the first time that an experimental vaccine made from a patient's tumor can spur the immune system to fight his prostate cancer.
The vaccine was tested in a group of men who had their prostates surgically removed but whose disease had spread to adjacent lymph nodes. This is the first sign of metastatic prostate cancer, which proves fatal in the vast majority of cases.
Dr. Jonathan Simons, who led the study, said that further research will be needed to see whether the vaccine is capable of bringing cancer into remission -- or better yet, of curing the disease. But he said the experiment was an important step, showing that a vaccine can trigger the immune system to fight cancer in the manner that it fights infection.
"For years, people have said there's no way to turn the immune system against prostate cancer," Simons said. "We were astounded to find that every part of the immune system was alerted and turned on."
Simons said the experiment produced a more comprehensive attack than anyone had expected, provoking not only the release of T-cells, as he had hoped, but also the production of antibodies against cancer. Both are key weapons of the immune system.
As scientists eye the future of cancer therapy, many consider vaccines to be among the two or three treatments that show the most promise. Vaccines are also being tried against other cancers, including melanoma and brain cancer.
In theory, vaccines would be more effective and less toxic than conventional therapies. Vaccines are generally viewed as a weapon that could be used with chemotherapy, radiation and surgery.
Despite the encouraging results, Simons said experiments like his should be viewed with caution.
"We absolutely do not have a cure by any stretch," he said.
Prostate cancer strikes about 330,000 men in the United States each year. New therapies are needed for the 40,000 men who die each year because their cancer has spread beyond the prostate to lymph nodes, bones and vital organs. It is the fourth-leading cancer killer in the United States, after cancers of the lung, colon and breast.
In the experiment, reported in this month's Cancer Research, Hopkins scientists injected a genetically altered cancer vaccine into 11 patients whose cancer had spread despite the removal of their prostate. Each vaccine was custom-made from the patient's tumor.
