Most chemotherapy drugs work by attacking fast-dividing cells. That's why they can make patients feel so sick — they destroy healthy cells alongside the cancer ones. But what if there were another way?
Researchers at Fox Chase Cancer Center in Philadelphia think they may have found one. Their new study suggests that adding a common thyroid hormone to standard chemotherapy could help prevent the most common malignant brain tumor in children from coming back. The tumor, called medulloblastoma, returns in up to 30% of young patients even after aggressive treatment.
The hormone is called triiodothyronine, or T3 for short. You might know it as a treatment for hypothyroidism, a condition where the thyroid gland doesn't make enough hormone. It's been approved by the FDA for decades. But Dr. Zengjie Yang and his team have discovered it might do something unexpected: help stop brain tumors from growing back after treatment.
In laboratory tests and mouse models, chemotherapy followed by T3 suppressed tumor growth more effectively than chemotherapy alone. It even worked against cancer cells that had become resistant to chemo. Most importantly, tumors that were treated with both therapies did not return after treatment ended, while tumors treated with chemo only eventually came back.
How does it work? The team used a strategy called differentiation therapy. Instead of trying to kill the tumor cells directly, T3 pushes them to mature into a normal-like state where they stop multiplying. "Differentiation is essentially cell maturation," Yang explained. "Instead of killing tumor cells directly, we push them to grow into mature cells that no longer multiply."
Because medulloblastoma mostly affects children, the researchers carefully studied whether T3 was safe. They found that T3 caused only a brief, mild increase in heart rate that was easily controlled with propranolol, a common blood pressure medication. The beta-blocker did not reduce T3's anti-tumor effects.
"This showed us that potential side effects are manageable using existing medications," Yang said.
Because T3 is already FDA-approved, inexpensive, and well understood, this approach could reach patients much faster than brand-new cancer drugs typically do. A multicenter pediatric clinical trial is now underway, funded by the Pediatric Neuro-Oncology Consortium, a national network of children's hospitals. The trial will test whether adding T3 to standard treatment can safely improve outcomes for children with medulloblastoma.
"Chemotherapy reduces tumor size by killing cells," Yang said. "T3 helps prevent the remaining cells from coming back. Together, they may offer children a better chance at long-term survival with fewer side effects."