A concentrated dose of a measles virus administered to a 49-year-old Minnesota woman with incurable cancer has put her disease in remission, doctors are reporting.

Stacy Erholtz, who has been battling a cancer of the bloodstream known as multiple myeloma, has seen the cancer relapse again and again in the past despite stem cell transplants and multiple bouts of chemotherapy.

Researchers at the Mayo Clinic have given Erholtz and another patient with the same cancer highly concentrated doses of a laboratory-engineered measles virus.

They engineered the virus to make it toxic to just cancer cells.

In a treatment known as virotherapy, Erholtz received a dosage level of enough of the measles virus to create measles vaccinations for 10 million people, the doctors said.

"The idea here is that a virus can be trained to specifically damage a cancer and to leave other tissues in the body unharmed," lead researcher Dr. Stephen Russell said.

Virotherapy has been used to treat thousands of cancer cases, but this marked the first time it resulted in a remission of a cancer type that had already spread throughout a patient's body, he said.

"I think we succeeded because we pushed the dose higher than others have pushed it," Russell said. "And I think that is critical. The amount of virus that's in the bloodstream really is the driver of how much gets into the tumors."

Although Erholtz's cancer went into remission, the virotherapy was not as successful for the other patient in the trial whose cancer returned after nine months, the researchers acknowledged.

Scientists at the Mayo Clinic say they're preparing a second-stage clinical trial that will involve more patients and have set a goal of FDA approval of the virotherapy treatment in four years.

They report they've been testing the measles virus's effectiveness with other cancers, including brain, neck and head cancers, as well as ovarian cancer and mesothelioma.

The goal of the research is a single-shot treatment as a cure for cancers, Russell said.

"It's like a call to action. It's not just good for our virus," he said of Erholtz's remission. "It's good for every virus everybody's developing as a cancer therapy. We know this can happen."