AURORA, Colo. – A Colorado grandfather diagnosed with terminal cancer is making a miraculous recovery.

Bill Brennan was first diagnosed with lymphoma about 10 years ago. It didn’t become active until 2017, at which point he underwent chemotherapy. He went into remission, but the cancer came back in February 2018.

I immediately thought, it’s over,” the 81-year-old Brennan told FOX31.

At that point, doctors at UCHealth University of Colorado Hospital told Brennan his only option was a new therapy called CAR-T cell therapy.

CAR-T uses the patient’s own immune system cells to attack and kill cancer cells.

“We remove T-cells or immune cells from the patients and we genetically modify them so we reeducate them to see the tumor and then we reinfuse those cells back into patients,” said Dr. Terry Fry, Director of Cancer Immunotherapy at the University of Colorado School of Medicine and Children’s Hospital at CU Anschutz Medical Campus.

T-cells collected from the patient are transported to a facility that genetically modifies the cells. The cells are then left to grow and multiply in specialized incubators. The process takes 10 to 14 days to complete.

The transformed cells are called CAR-T cells. Once reinjected into the patient, CAR-T cells are designed to seek out a protein specific to cancer cells. Each batch made is engineered specifically for each patient.

The FDA approved two commercial versions of CAR-T cell therapy in August 2017. It is also being tested in clinical trials at places like UCHealth.

So far, doctors say the results are “unheard of”. According to Dr. Fry, a clinical trial is considered successful and “really effective” if it tumors shrink in 10 to 30 percent of patients.

“With CD-19 targeted T-cells, the ones that are commercially approved, there was an 80 to 90 percent complete remission reduction rate in patients that had essentially exhausted all other options,” Dr. Fry said.

Brennan is part of that statistic. Twenty-eight days after being injected with his CAR-T cells, his PET scan showed he was cancer free.

“You’re absolutely looking at a miracle. And that’s the way I feel,” Brennan said.

UCHealth is one of only a handful of hospitals nationwide using CAR-T cell therapy. The CU Anschutz Medical Campus is also one of only a handful of facilities capable of manufacturing the modified cells.

“There are probably less than a dozen in the country that have the capabilities that we have here and definitely the only one in this region,” Ryan Crisman, Director of Cell Processing at the Gates Biomanufacturing Facility, said.

The process is labor intensive since the product can not be mass produced. The facility can manufacture CAR-T cells for up to five patients at one time. And there is a shortage of qualified workers.

The Gates Biomanufacturing Facility is unique though, in that a patient at UCHealth can have their cancer medication manufactured in a laboratory in a building across campus.

While the potential of CAR-T cell therapy gives hope to patients like Brennan, it has its limitation. Right now, it is only approved for use in treating cancers of the blood like leukemia and lymphoma. It can be cost prohibitive, it isn’t widely available yet and the future for patients is unknown.

“What we now know is that out of all those patients who go into remission, probably half will relapse within a year,” Dr. Fry said.

He also says that once a patient has been treated with CAR-T cell therapy, leukemia becomes resistant to it.

“We should all realize that we’re very early on in this game,” he said.

There is a lot of research left to do on CAR-T cell therapy and its potential uses in treating cancers. Experts believe it could eventually be a game-changing treatment for cancer patients.

“I think there is a lot of potential for this therapy beyond that specific type of cancer,” Fry said. “There’s a lot of work being done to try to develop CAR-T cells for other types of cancer, solid tumors included.”