Radiotherapy is essential for treating pediatric brain tumors, but the treatment comes with the risk of cognitive impairment. Researchers at Baylor College of Medicine, Texas Children’s Hospital and the Hospital for Sick Children (SickKids) in Toronto examined children treated with two different kinds of radiotherapy—proton radiotherapy and photon radiotherapy—and found those treated with proton radiotherapy had less intellectual decline. Their results are published today in the Journal of Clinical Oncology.

The study focused on patients with pediatric medulloblastoma. A group at Texas Children’s Cancer Center was treated with proton radiotherapy, and a group of patients at SickKids was treated with photon radiotherapy. The dose of radiation to healthy tissue is lower with proton radiotherapy than with photon radiotherapy.

Researchers examined changes in patients’ intelligence scores over time. The proton radiotherapy group had stable Global IQ and working memory scores while the photon radiotherapy group showed a decline in both domains. Proton radiotherapy patients also showed higher perceptual reasoning scores compared to photon radiotherapy patients. Patients in both treatment groups showed declines in processing speed over time. Researchers also noted that while proton radiotherapy scores were higher, newer photon radiotherapy techniques also yielded higher scores than older techniques.

“Our findings provide a message of hope. The outcomes for both groups are superior to outcomes reported for children treated several decades ago, thanks to refinement of radiotherapy techniques,” said Dr. Lisa Kahalley, co-principal investigator, first author of the study and associate professor of pediatrics – psychology at Baylor College of Medicine. “Still, our findings show a clear cognitive benefit with proton radiotherapy.”

Despite the promise of proton radiotherapy, the treatment is not widely available, according to Kahalley, director of psychology research at Texas Children’s Hospital and member of the Dan L Duncan Comprehensive Cancer Center at Baylor. Proton radiotherapy is more costly than photon radiotherapy and oftentimes is not covered by insurance.

“If studies continue to demonstrate that proton radiotherapy offers medical and quality of life benefits that are superior to photon radiotherapy, we will need to address barriers to access for pediatric brain tumor patients,” Kahalley said.

“While progress has been made in treating children with brain tumors, this often comes with a host of costs including chronic health conditions and learning challenges,” said Dr. Donald Mabbott, co-principal investigator and psychologist, senior scientist and head of the Neurosciences and Mental Health Program at SickKids. “We are working to find ways to mitigate these challenges for cancer survivors.”

Other contributors to this work include Drs. Rachel Peterson, M. Douglas Ris, Laura Janzen, M. Fatih Okcu, David R. Grosshans, Vijay Ramaswamy, Arnold C. Paulino, David Hodgson, Anita Mahajan, Derek S. Tsang, Normand Laperriere, William E. Whitehead, Robert C. Dauser, Michael D. Taylor, Heather M. Conklin, Murali Chintagumpala, and Eric Bouffet. The authors are affiliated with the following institutions: Baylor College of Medicine, the Hospital for Sick Children (SickKids), the University of Texas MD Anderson Cancer Center, the University of Toronto, Princess Margaret Cancer Centre, the Mayo Clinic and St. Jude’s Research Hospital.

This work was supported by the National Institutes of Health/National Cancer Institute (grants R01CA187202 to LSK and K07CA157923 to LSK) and the Canadian Institute of Health Research (MOP-123537 to DJM) and SickKids Foundation.