Cancer researchers are excited about the prospect of someday treating bone marrow cancer using a measles virus that seems well matched for the job.

Two research subjects, a 49-year-old woman and a 65-year-old woman, were given a massive dose of measles virus intravenously to fight their multiple myeloma, a bone marrow cancer that can also cause skeletal or soft tissue tumours.

Stacey Erholtz of Minnesota didn’t respond to conventional or stem cell treatments. When she enrolled in the experimental trial, researchers say she experienced remission for more than six months.

"I think it’s remarkable," Erholtz said in a hospital video. "Who would have thought?"

Dr. Stephen Russell, a hematologist at the Mayo Clinic in Rochester, Minn., treated Erholtz and the other patient, whose response to the treatment was more short-lived.

"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," Russell told Reuters Health. "We haven’t discovered a cure for cancer here."

In the journal Mayo Clinic Proceedings, Russell and his team describe how they gave the two women an extremely high dose of the measles vaccine engineered to kill cancer.

"It was single intraveneous infusion of measles virus," Russell said in another hospital video. "The tumour on her forehead regressed completely. The other lesions that were visible on her PET CT scan disappeared completely."

Side-effects included fever, vomiting, shivers and severe headache.

Four other patients who were treated did not respond, Reuters reported.

At his lab at the Ottawa Hospital Research Institute, John Bell is also testing cancer-fighting viruses, known as oncolytics, in animals. He called Russell’s observations exciting and a nice demonstration.

"By combining just the right virus with the right kind of cancer we're getting these such stellar responses, and that's where this field has to head next," said Bell, who wrote a journal commentary on the study. "We have to figure out which viruses with which kinds of cancer or which people would work best."

The Mayo Clinic is planning a larger clinical trial. If those results are favourable and the response lasts then regulators could consider approving it.