When Maddie Demers’ rare metastatic bone cancer stopped responding to conventional chemotherapy in June, her oncologist advised the young girl’s parents, Barbie and Mike, to put her under hospice care. But today, after receiving three rounds of a targeted radiation traditionally used to treat prostate cancer, bone scans suggest the cancer has stopped spreading.

“We’re steadily reducing her disease burden, and it may not cure her, but it’s made her a lot better,” Dr. Peter Anderson, Maddie’s oncologist at Cleveland Clinic Children’s, told FoxNews.com.

The treatment, called radium, targets the growth of new bone, which aligns with the spread of cancer. After suffering from a persistent leg ache, Maddie, an outgoing 10-year-old who was the captain of her school’s cheerleading squad, was diagnosed in early May with multicentric osteogenic sarcoma, a bone cancer so rare that most doctors never see a case in their lifetime. By the time she received a leg biopsy in Orlando, about 125 miles northwest of her hometown, Port St. Lucie, the disease had spread to her pelvis and spine. Doctors promptly started her on aggressive chemotherapy treatment but gave her only 15 months to live.

“I was already looking for doctors when they told us it was extremely rare bone cancer,” Barbie, 41, told FoxNews.com. “I had a friend of mine who was searching all the outlets she [could], and that’s when we found Dr. Anderson.”

When she called Anderson, who has been studying osteosarcoma since the mid-1980s, he recommended the same 10 rounds of the chemotherapy prescribed by Maddie’s doctors in Orlando, so the family moved forward with that plan. But five weeks into the regimen, a CT scan revealed treatment wasn’t working— Maddie’s cancer had spread to her lungs. Doctors recommended ending treatment and putting her under hospice care, Barbie recalled.

“I went back into [the room] where Maddie was and called Dr. Anderson … and I said, ‘We need to come there,’” said Barbie, who next relayed the unexpected turn of events to Anderson. “He said, ‘Be here by Friday.’”

The family took an air ambulance to the Cleveland Clinic, where Anderson placed Maddie on a 14-day chemotherapy drip and accompanying chemo pill, put her on a morphine drip, and cast and put nerve blockers in her leg to help ease the pain.

When Anderson suggested radium, Barbie’s mind flashed back to her early online research of Anderson, as well as a conversation she had with another patient’s parent in Orlando.

“Somebody (the parent) said to me, ‘Dr. Anderson used to be at MD Anderson [Cancer Center]. My daughter was diagnosed with osteosarcoma and was given grim chances, and he saved her life.’ That clicked into my head,” Barbie said. “This is a rare cancer that nobody’s heard of and she’s got so many tumors, it can’t hurt. So when he said, ‘This is what we want to try,’ I said, ‘Absolutely, of course.’”

Maddie has undergone three monthly rounds of the radium, and each injection is infused over one minute. She has three more rounds of the treatment to go for a total of six injections, a regimen that follows the typical treatment for prostate cancer and is slated to end in time for the holidays. Side effects of radium include an upset stomach and fleeting pain, the latter of which Maddie has experienced. Anderson has studied radium in osteosarcoma patients before, but he said Maddie is the youngest osteosarcoma patient he knows of who has received the drug.

Using sodium fluoride to detect where cancer is spreading, a PET scan suggests the radium has helped eradicate cancer cells in multiple areas of Maddie’s bone, including her skull base and the top of her spine.

“We would hope as we continue to do this her quality of life will stay good, and it’s something that would set her up for being on a chronic but tolerable medical regimen,” Anderson said. “It’s a temporary solution, and if there’s new treatments that would benefit her, we’d be the first to share that with her family.”

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If the radium ends up failing, Anderson said he’d look to use a drug called muramyl tripeptide phosphatidyl ethanolamine (MTP-PE), which is not approved in the United States but is available in other countries such as Mexico, Europe, Taiwan and Israel, and has proven to extend osteosarcoma patients’ lifespan. He said he would also turn to a new class of drugs, immune checkpoint inhibitors, which are showing some promise for melanoma, and a type of oral gene therapy being developed by Ococeutics, a drug discovery and development company.

“With Maddie, I would say all bets are off on her— she’s doing better than expected,” said Anderson, who added that Maddie is currently being treated on an outpatient basis.

Dr. Kurt Richard Weiss, an assistant professor at the University of Pittsburgh School of Medicine Department of Orthopaedic Surgery, Division of Musculoskeletal Oncology, and director of the Cancer Stem Cell Laboratory, said as a 15-year-old in 1999 he was cured of osteosarcoma with MTP-PE, which was being studied in a phase II trial at MD Anderson. After a phase III trial to confirm its efficacy, the Food and Drug Administration was not satisfied with the data presented, so it didn’t approve the drug.

But Weiss, who now operates on osteosarcoma patients, knows the power of experimental therapy in helping to save lives. He predicted immunotherapy would make waves in osteosarcoma treatment due to the cancer’s predictable nature of spreading to the lungs. Types of immunotherapy vary, but generally the treatment harnesses the immune system’s natural ability to destroy cancer cells. The therapy is at the forefront of cancer research today.

Although he hasn’t studied radium in a scientific setting, Weiss, said the drug appears to show promise too.

“Radiation has a poor track record with bone sarcomas … but [radium] is a different animal,” he told FoxNews.com. “This is getting the radiation to the bone from the inside rather than the outside, so it’s an interesting twist on how to do that.”

Weiss previously worked with Anderson and at MD Anderson, but he has not treated Maddie.

Maddie has weekly checkups with Anderson at the Cleveland Clinic, where she has blood work done. To rebuild her strength, she undergoes physical therapy two times a week. Recently, she walked 100 feet with her walker— a task made more challenging due to the leg biopsy in Orlando. Despite the physical discomfort, Maddie is a fighter, her mother said.

The day she was diagnosed, Barbie recalled, she had to explain to Maddie the importance of staying strong throughout this battle.

“I explained to her that, ‘You gotta fight; you can be pissed off and mad all you want, and have bad days, but the one thing we ask from you is to fight,” Barbie said. “And the girl fights, and she’s been fighting since.”

To learn more about Maddie's fight, visit her website, MaddiesFight.com. To support her family in covering her medical bills, visit Maddie's GoFundMe page.