ESTRO 38: What Type of Radiotherapy May Best Preserve Cognitive Function in Pediatric Patients With Brain Tumors?
A comparison of three types of radiotherapy for pediatric brain tumors suggests that a type of proton therapy called pencil-beam scanning (PBS) offers the best hope of preserving cognitive functions. The study, presented by Toussaint et al at ESTRO 38, the annual congress of the European Society for Radiotherapy & Oncology (ESTRO), showed that this new form of radiotherapy delivers the lowest doses of radiation to the temporal lobes and hippocampus, areas of the brain that are important to functions like memory (Abstract OC-0670).
The study was presented by Laura Toussaint, a PhD student in the Department of Medical Physics, Aarhus University Hospital, Denmark. She said, “Brain tumors are the second most common type of cancer in children. Survival rates have increased in recent decades, and currently, 75% of children diagnosed with a brain tumor will be alive 5 years later. Alongside surgery and chemotherapy, radiotherapy plays an important role in treating brain tumors in children, but we need to protect children’s developing brains from any unnecessary radiation. The more we learn about how to effectively target brain tumors while minimizing the dose to other parts of the brain, the better we can preserve children’s cognitive abilities and quality of life after treatment.”
Study Methods
Ms. Toussaint and her colleagues carried out detailed studies of 10 different children treated for brain tumors. Each child had been diagnosed with a type of cancer called craniopharyngioma, centrally located in their brain. For each child, researchers planned treatments with each of the three types of radiotherapy: volumetric modulated arc therapy (VMAT), double-scattering proton therapy (DSPT), or PBS. All three are advanced radiotherapy treatments, but DSPT and PBS are both types of proton therapy, which research suggests is better at targeting the tumor more precisely while sparing the surrounding tissues. However, they require expensive specific equipment, which is not yet available in all hospitals. PBS is an especially precise form of radiotherapy that delivers treatment via a very narrow proton beam.
Previous research has shown that radiation doses to particular areas of the brain, including the temporal lobes and hippocampus, have an impact on children’s cognitive outcomes, specifically in memory functions. Toussaint and her colleagues used these existing data to select 30 structures in the children’s brains to study.
The researchers used computed tomography and magnetic resonance imaging to precisely locate the structures in each of the children’s brains. Then they compared the 3 treatment plans for each child to see which type of treatment was better at sparing those 30 structures from radiation, categorizing the dose to each structure as high, medium, or low.
Results
The research team found that the doses to the temporal lobe were lower with the PBS treatment compared to both the DSPT and VMAT treatments. They found that 41% of the left hippocampus volume was receiving low doses of radiation with the DSPT plans, whereas 0% was receiving low doses with the PBS treatment; 43% of the amygdala was receiving low doses of radiation with DSPT vs 24% with PBS. For the brain structures associated with cognition located outside of the temporal lobes, the volumes exposed to low doses were in general smaller with both proton modalities compared to VMAT, whereas intermediate and higher dose levels to the ventricular substructures were reduced in the VMAT plans due to field configurations for both DSPT and PBS.
Using the existing data on the impact of radiation to these regions of the brain, the researchers predict that the proton therapies, particularly the PBS treatment, would result in less impairment of the children’s memory function.
Ms. Toussaint said, “We have looked at three types of radiotherapy, which all aim to successfully treat brain tumors while doing as little damage to children’s brains as possible. What we found was that pencil-beam scanning proton therapy seems to be by far the best at avoiding parts of the brain that are important in children’s memory. The next step would be to confirm this finding with clinical research in patients.”
Disclosure: For full disclosures of the study authors, visit estro.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
