Poliovirus once terrorized the world, infecting and paralyzing hundreds of thousands of people, but it may now play a vital role in battling cancer, according to new findings published in the New England Journal of Medicine.

According to the report, which was discussed at a conference in Norway on Tuesday, patients with brain tumors who were given genetically modified poliovirus had a better long-term survival rate as it helped their bodies attack the cancer.

This was the first human trial for this concept, and while it didn’t help most patients or improve average survival rates, it did help some in a big way — about 21% who responded well to the test were alive at the three-year mark, in comparison to 4% of those in the comparison group.

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"This is really a first step," Duke University's Dr. Annick Desjardins told the Associated Press.

Polio remains endemic in only three countries: Afghanistan, Nigeria, and Pakistan. There were 22 cases of wild polio in 2017 and there have been 11 so far in 2018. It is a highly infectious disease that affects the nervous system and can cause paralysis.

Because the poliovirus initiates such a strong response from the immune system, researchers thought they might be able to use as a weapon against cancer. Doctors at Duke and the National Cancer Institute worked together to genetically modify the poliovirus so that it would infect tumor cells, but not hurt nerves, AP reported.

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The treatment is inserted into the brain. Because the immune system will identify it as a virus, it will begin to attack the brain tumor.

The adapted poliovirus was tested on 61 patients with tumors that had persisted after initial treatments. The median survival was about a year, which was similar to the other group receiving different treatments, but after two years, there were improvements in the patients given the poliovirus.

While these tests are still preliminary, survival is currently estimated at 21% at the two- and three-year marks versus 14% for the other group at two years, and just 4% for three years.

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The study’s first patient, Stephanie Hopper, was treated  in May 2012. Since then, she has finished college and become a nurse. Recent scans showed no signs of an increase in the size of her tumor, Hopper told AP.

"I believe wholeheartedly that it was the cure for me. Most people wouldn't guess that I had brain cancer," she told AP.

While these tests are still in very early stages and the results are not yet overwhelmingly positive, cases like Hopper’s present glimmers of hope for future trials.

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While it is disappointing that the median survival was not improved, Dr. Howard Fine, brain tumor chief at New York-Presbyterian and Weill Cornell Medicine, said the "extraordinary responders, a small group of patients who have done markedly better than one would expect," were encouraging.

The evidence suggests the testing is worthy of more research, Fine told AP.

A second adult study that also utilizes chemotherapy is already underway, as is a study with children with brain tumors. Other planned studies include ones for breast and skin cancer.

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