Two and a half years ago, doctors told a Florida woman battling breast cancer that she had just three months to live.

Judy Perkins, 52, of Port St. Lucie, is now cancer free thanks to an experimental treatment that harnessed billions of her own immune cells, reported the BBC.

Perkins had a mastectomy and all her lymph nodes removed and went through chemotherapy and hormonal therapy. When all those methods failed to halt the spread of cancer to her chest and liver, she was sure she was going to die — that is, until she met Dr. Steven Rosenberg at the National Institutes of Health.

Rosenberg studied Perkins’ immune cells, finding those white blood cells capable of detecting genetic mutations and fighting cancer. Scientists then extracted those cells and grew them in a lab before injecting her with 90 billion of them.

“I think it had been maybe 10 days since I’d gotten the cells, and I could already feel that tumor starting to get soft,” Perkins told CBS. “By then I was like, ‘Dang, this is really working.'”

Rosenberg believes Perkins’ cells are still working to keep her cancer free.

“Circulating in her body are large numbers of cells we administered to her two and half years ago,” he said.

“This is just one treatment that’s necessary because the cells are alive. They’re part of Judy. They are Judy Perkins.”

Perkins signed up for Rosenberg’s cancer trial knowing there were risks involved. She sent two of her friends with cancer to Rosenberg’s lab for the same treatment and both of them died, NBC reported.

Rosenberg, who takes on patients with particularly aggressive cancers or just months to live, knows the treatment is not yet ready for widespread use but believes it could pave the way for treatment of several different cancers.

“A lot of works needs to be done, but the potential exists for a paradigm shift in cancer therapy — a unique drug for every cancer patient — it is very different to any other kind of treatment,” Rosenberg told the BBC.