Intellectual sparing in children with rare brain cancer: New research demonstrates better cognitive outcomes with less invasive treatment for paediatric medulloblastoma

TORONTO - For decades, there has been mounting interest in the potential of novel and effective treatments – that can also spare brain function – for a rare, yet devastating paediatric brain cancer called medulloblastoma.

New research findings by scientists at The Hospital for Sick Children (SickKids), Baylor College of Medicine and Texas Children’s Hospital offer evidence that a new type of radiation therapy can effectively treat the tumour without causing the level of impairment to the brain that is usually caused by standard treatments. The study was published today in the Journal of Clinical Oncology.

“Medulloblastoma is a devastating tumour in terms of long-term late effects from the disease and treatment that can be very aggressive compared to other types of paediatric cancer,” says Dr. Donald Mabbott, co-principal investigator of the study and Psychologist, Program Head and Senior Scientist in the Neurosciences & Mental Health Program at SickKids. “The most common and available treatment is photon radiation to the entire brain and spine. Our study found that an alternative approach called proton radiotherapy can offer less damaging effects by sparing healthy regions of the brain, thus leading to better intellectual outcomes in children post-treatment.”

In the study, researchers compared intellectual outcomes of children with medulloblastoma treated with proton radiotherapy (PRT) at Texas Children’s Hospital – where it is standard of care – versus children treated with the photon (or x-ray) radiotherapy (XRT) at SickKids. Proton radiotherapy is not currently available in Canada.  

The results showed that PRT was associated with significant sparing of brain function in global IQ, perceptual reasoning, and working memory that was not observed in children treated with XRT.

At a four-year follow up, on average, children treated with PRT exhibited superior intellectual outcomes in all domains (except processing speed) compared to those treated with XRT. This is the first longitudinal study to compare this change over time.

Brain regions affected in children treated with photon (x-ray) radiotherapy (XRT) (left) compared with proton radiotherapy (PRT) (right)

“We know that radiotherapy is essential for treating certain paediatric brain tumours, but we also know it comes with cognitive risks,” says Dr. Lisa Kahalley, lead author of the study and Associate Professor and Director of Research Psychology Section, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital. “Our research findings provide a message of hope. The outcomes for both groups were superior to the outcomes reported for children treated several decades ago, thanks to refinement of radiotherapy techniques. This is the first rigorous study to show that PRT can result in better cognitive outcomes in children with medulloblastoma compared to modern photon radiotherapy.”

Medulloblastoma is one of the most common childhood malignant brain tumours. It originates within the brainstem or the cerebellum. With advances in treatment, the majority of children go into remission. The tumour and treatment can lead to physical, neurological and neuropsychological disabilities that can manifest acutely after treatment and persist into adulthood.

“While significant progress has been made in treating children with brain tumours, this often comes with a host of costs including chronic health conditions and learning challenges,” says Mabbott. “Our study provides the strongest evidence to date that demonstrates proton radiotherapy’s long-term medical and quality-of- life benefits in the treatment of paediatric medulloblastoma.”

This work was supported by the National Institutes of Health/National Cancer Institute, Canadian Institute of Health Research, and SickKids Foundation.