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The normal dose of vaccine contains 10,000 infectious units of the measles virus, Russell said. Mayo started out giving patients 1 million infectious units and gradually cranked up the dosage — but it didn’t work until Erholtz and another patient were injected with 100 billion infectious units, he said.
While the treatment worked in Erholtz, whose tumors were primarily in her bone marrow, the results weren’t sustained in the second patient, whose tumors were largely confined to her leg muscles. Russell said researchers need to study how the nature of the tumor affects the lethality of the virus.
“I think if we had been able to give bigger dose, we might have got a better outcome in that second patient,” he said.
But at least for now, there’s no second chance. Once the vaccine has been delivered, the body’s immune system will recognize it and attack it. Russell said breaking down the immune system before the treatment will be part of another upcoming clinical trial.
Researchers also may be able to bypass the immune system by taking a patient’s cells and converting them into Trojan horses. The virus is loaded into the cells, and they are injected back into the bloodstream. “That way it doesn’t get destroyed before it reaches its target,” Russell said.
Close to success
At the James Cancer Hospital and Solove Research Institute in Ohio, Dr. Tanios Bekaii-Saab is working on a study to treat pancreatic cancer using Reolysin, a proprietary variant of the virus that causes the common cold.
Researchers, he said, have two primary approaches: Inject the virus directly into tumors to get past their defenses or inject it into the bloodstream and hope it will seek out tumors and overwhelm them, as was done in the Mayo study.
Saab said he expects one of these virus “platforms” is likely to become standard treatment for a cancer such as myeloma or pancreatic cancer within three to four years.
After reading a draft of the Mayo study, Saab called it “an incredibly innovative way to actually attack the cancer and perhaps even offer a better chance at complete remission,” especially in combination with radioactive molecules and immune system therapy.
He cautioned that the study still must be confirmed in large randomized clinical trials — the point where many hopes get dashed.
“Unless we get to the third stage of development, we are only cautiously optimistic,” Saab said.
For her part, Erholtz has no regrets about participating in the study and remains optimistic that she will remain cancer-free at her annual checkup next month in Rochester.
“We don’t let the cancer cloud hang over our house, let’s put it that way, or we would have lived in the dark the last 10 years,” Erholtz said.
Dan Browning • 612-673-4493