Mayo Clinic researchers stirred excitement on Thursday by saying they had treated a patient's blood cancer with a specially engineered measles virus, but even scientists involved in the work caution the response does not prove they have a cure.
Many failed cancer drug trials involving hundreds or thousands of patients include results from "outliers" whose disease subsided inexplicably. So while the method employed by Mayo may provide a promising lead for study, it has to be corroborated in many more cases, they noted.
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“We have an enormous amount of work to do to determine if this is generalizable and how to best apply the approach to other cancer patients," said Dr. Stephen Russell, the report's lead author and a hematologist at the Mayo Clinic in Rochester, Minnesota. “We haven’t discovered a cure for cancer here."
He and his colleagues write in the journal Mayo Clinic Proceedings that multiple myeloma in a 49-year-old woman seemed to disappear after she received an extremely high-dose injection of a measles virus engineered to kill the cancer cells.
Multiple myeloma affects immune cells called plasma cells, which concentrate in the soft tissue, or marrow, inside bones.
A second woman also with multiple myeloma began responding to the therapy, but her cancer eventually returned. Four other patients who received the high-dose therapy had no response.
“You never know whether it’s really what the person received from the measles virus or something we don’t understand,” said William Phelps, program director at the American Cancer Society, who was not involved in the new research.
Russell and colleagues believe the two women who showed some response had few or no circulating measles antibodies, which might eliminate the engineered virus before it has a chance to kill the cancer cells. The therapy will now enter a mid-stage trial to see whether more patients with low circulating antibodies respond to high-doses of the virus, he said.
“There are many patients who would like this treatment tomorrow, but that’s not possible,” Russell said.