ASTRO: Proton Therapy Yields Encouraging Outcomes for Pediatric Brain Tumor Patients
When used to treat pediatric patients with intracranial malignant tumors, proton therapy may limit the toxicity of radiation therapy while preserving tumor control, according to research presented on Sunday, September 22, at the American Society for Radiation Oncology’s 55th Annual Meeting (Abstract 2188).
Typically, central nervous system malignancies are treated with surgical resection and postoperative radiation therapy. Proton therapy, an external beam radiation therapy in which protons deliver precise radiation doses to a tumor, offers significant sparing of healthy tissues outside the target region, compared to conventional photon radiotherapy. Proton therapy is frequently used to treat central nervous system malignancies in young children in order to minimize the amount of radiation exposure to their still-developing brain. Although this therapy holds great promise, to date, published clinical data are limited.
Study Details
This study evaluated 70 patients with localized ependymoma, a relatively common childhood cancer—the largest reported group of pediatric patients treated with proton therapy. The patients in the study ranged in age from 1 to 20 years and were all treated with involved-field proton radiation at the Massachusetts General Hospital in Boston from October 2000 to February 2011. Forty-six of the patients (66%) had a gross total resection, and 24 patients (34%) had a subtotal resection.
Upon patient follow-up at 46 months after proton therapy treatment, the 3-year local control was 83%, progression-free survival was 76%, and overall survival was 95%. The researchers found that subtotal resection surgery correlated with decreased progression-free survival (54%) and overall survival (90%), compared to the patients who underwent complete tumor removal prior to proton therapy, who had a progression-free survival of 88% and an overall survival of 97%.
Cognitive and Endocrine Outcomes
In addition to survival outcomes, cognitive and endocrine outcomes were analyzed. Neuropsychological assessments were administered before and after proton therapy to measure total intelligence quotient (IQ). Scales of Independent Behavior (SIB-R), a written questionnaire that assessed functional independence, were completed by the patients’ parents. Within a subset of 14 of the patients, the average IQ was 108.5 at baseline, and 111.3 after 2 years of follow-up. In a larger group of 28 of the patients, overall SIB-R score was 100.1 at baseline, and 100.8 after 2 years of follow-up. It was also noted that few patients developed evidence of growth hormone deficiency, hypothyroidism, or hearing loss.
“This study represents the best available evidence on the use of proton radiotherapy in the pediatric population,” said Shannon MacDonald, MD, the principal investigator of the study, a pediatric radiation oncologist at the Massachusetts General Hospital. “Our analysis is the first to present auditory, endocrine, and cognitive outcomes, the domains expected to benefit from this highly streamlined form of radiation therapy. Given the increasing numbers of proton facilities and the high cost of proton treatment, this data was urgently needed to provide evidence-based guidance on proton therapy outcomes for pediatric brain tumor patients.”
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®.
