The study, published in The Lancet Oncology, suggests proton beam therapy is as effective as other treatments.
Researchers looked at 59 patients aged between three and 21 from 2003 to 2009.
In 2014 the parents of Ashya King took him out of hospital in Hampshire to get the treatment abroad.
Their actions led to a police operation to find them.
Ashya, who was five at the time of his treatment, is now cancer free, his family said last year.
All the patients who took part in the study, led by Dr Torunn Yock from the Massachusetts General Hospital in the US, had the most common kind of malignant brain tumour in children, known as medulloblastoma.
After five years, their survival rate was similar to that of patients treated with conventional X-ray radiotherapy, but there were fewer side effects to the heart and lungs, the study found.
Dr Yock told BBC Radio 5 live: “The major finding is that proton therapy is as effective as photon therapy [conventional X-ray radiotherapy] in curing these patients and what is also very exciting is that it is maintaining these high rates of cure but doing so with less late toxicity, which has dramatic quality of life improvements.”
The paper said: “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.”
What is proton beam therapy?
Animated graphic comparing traditional radiation treatment with proton beam therapy.
The treatment allows high-energy protons to be targeted directly at a tumour, reducing the dose to surrounding tissues and organs.
In general, it gives fewer side effects compared with high-energy X-ray treatments.