(EurekAlert!) – The use of proton radiotherapy to treat the most common malignant brain tumor in children is as effective as standard photon (x-ray) radiation therapy while causing fewer long-term side effects such as hearing loss and cognitive disorders, according to a study receiving online publication in Lancet Oncology. The paper from a team led by Massachusetts General Hospital (MGH) investigators describes patient outcomes an average of seven years after proton therapy for medulloblastoma, a fast-growing tumor that develops in the cerebellum at the base of the brain.
“Proton radiotherapy is still not widely available in the U.S. or around the world, but it is increasingly recognized for its potential to reduce the side effects of treatment, particularly in the pediatric population,” says Torunn Yock, MD, MCh, MGH Department of Radiation Oncology, lead and corresponding author of the report. “At experienced centers, proton therapy has a proven track record of treatment success and safety.”
In contrast to photon radiotherapy, in which a dose of radiation is delivered all along the x-ray beam as it passes through a patient’s body, in proton therapy the dose is precisely focused on the target area with little or no dose delivered to normal tissues in front of or behind the tumor. This feature has made proton therapy particularly attractive to treat tumors in or near the brain or eyes, areas where the protection of nearby healthy tissues is particularly critical.
While medulloblastoma can often be successfully treated with a combination of surgery, chemotherapy and radiotherapy, because of its location within the brain, long-term side effects are common. These can include hearing loss, which can be particularly problematic in young children; problems with learning and memory, and neuroendocrine disorders caused by irradiation of the pituitary gland and hypothalamus. Also commonly seen are problems affecting the heart, lungs, thyroid, spine and reproductive organs, all of which tend to be more serious in children treated at younger ages.
While proton therapy may appear to be ideal for reducing these adverse effects, no previous study had prospectively examined the long-term results of children treated for medulloblastoma with proton therapy. To investigate their hypothesis that proton therapy would reduce the incidence and severity of side effects without loss of treatment effectiveness, the researchers enrolled children and adolescents ages 3 to 21 – with an average age of around 6 ½ – who received proton therapy for medulloblastoma at the MGH from 2003 to 2009. All had previous surgery to remove as much of the tumor as possible, and all received chemotherapy before, during or after proton therapy.