Proton Beam Therapy Treats Childhood Brain Cancer as Effectively as Standard Radiation

Treating medulloblastoma with proton beam therapy results in survival rates that are equivalent to those with photon radiation therapy. Findings also suggest proton beam therapy treatment may result in fewer severe side effects in children according to phase 2, single-arm findings published in The Lancet Oncology.¹

Proton beam therapy is highly targeted and irradiates less normal tissue than conventional photon radiotherapy, suggesting it may have fewer toxic side effects for the body. Its precision could be important for medulloblastoma, the most common malignant childhood brain cancer. Medulloblastoma tumors spread through cerebrospinal fluid to additional locations along the surface of the brain and spinal cord. Conventional treatment of tumor removal surgery, photon radiotherapy, and chemotherapy can result in widespread side effects. These side effects include hearing loss, cognitive effects, and hormonal deregulation as well as effects on many major organs.

“Proton radiotherapy resulted in acceptable toxicity and had similar survival outcomes to those noted with conventional radiotherapy, suggesting that the use of the treatment may be an alternative to photon-based treatments,” the authors stated. The study was led by Torunn Yock, MD, Associate Professor at Harvard Medical School and Director of Pediatric Radiation Oncology at Massachusetts General Hospital in Boston, Massachusetts.

Between 2003 and 2009, Dr Yock and colleagues enrolled 59 patients aged 3 to 21 years with medulloblastoma in proton radiotherapy. All patients received chemotherapy, and most (55 patients) received partial or complete surgical removal of tumors. Follow-up lasted for an average of 7 years. All patients received chemotherapy.

Adverse events included hearing loss, hormonal deregulation, and cognitive effects. Hearing loss affected 12% of patients at 3 years and 16% of patients at 5 years. At 5 years, 55% of patients experienced problems with hormonal regulation, particularly with growth hormone. While perceptual reasoning and working memory remained unaffected at 5 years, patients had impaired processing speed and verbal comprehension.

Unlike conventional photon radiotherapy, the proton radiotherapy patients experienced no toxic effects in major organs and tissues. Progression-free survival was 83% at 3 years and 80% at 5 years.

“Our findings suggest that proton radiotherapy seems to result in an acceptable degree of toxicity and had similar survival outcomes to those achieved with photon-based radiotherapy,” stated the authors.

“Although there remain some effects of treatment on hearing, endocrine, and neurocognitive outcomes, particularly in younger patients, other late effects common in photon-treated patients, such as cardiac, pulmonary, and gastrointestinal toxic effects, were absent.”

The study was funded by the National Cancer Institute and Massachusetts General Hospital.

Reference

1. Yock TI, Yeap BY, Ebb DH, et al. Long-term toxic effects of proton radiotherapy for paediatric medulloblastoma: a phase 2 single-arm study [published online ahead of print January 29, 2016]. Lancet Oncol. doi: 10.1016/S1470-2045(15)00167-9.