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Beam therapy hope for childhood cancer treatment

Fewer side effects from proton beam therapy

Adrian O'Dowd

Monday, 01 February 2016

Using proton beam therapy – a more precise form of radiotherapy – to treat the most common malignant brain cancer in children could be just as safe as using conventional radiotherapy, according to research* published in The Lancet Oncology journal at the weekend.

US researchers found that using proton beam therapy to treat the childhood brain cancer medulloblastoma appeared to be no more hazardous than conventional radiotherapy with similar survival rates and fewer severe side effects.

Medulloblastoma, which involves rapidly growing tumours, develops at the rear and base of the brain, near the bottom of the skull.

Conventional treatment usually involves surgery to remove the tumour, photon radiotherapy and chemotherapy.

However, patients are often left with significant side effects including hearing loss, effects on cognition, hormone function as well as toxic effects on the heart, lungs, thyroid, vertebra and reproductive organs as a result of healthy bodily tissues being exposed to radiation.

Compared with traditional radiotherapy, proton beam therapy is highly targeted and is used to treat hard-to-reach cancers, with a lower risk of damaging the surrounding tissue and causing side effects.

Proton beam therapy was highlighted in the news in 2014 when UK parents Brett and Naghmeh King took their son Ashya from Southampton General Hospital, without doctors’ permission so that he could be treated with proton beam therapy in Prague in the Czech Republic.

At the time, proton beam therapy was not available on the NHS, although the NHS later agreed to fund his treatment. UK centres for proton beam therapy are currently being planned.

The study, led by Dr Torunn Yock of the Massachusetts General Hospital, Proton Center, Boston, USA, and colleagues, involved 59 patients aged 3 to 21.

Most of the patients (55) had the tumour partially or completely removed through surgery.

All patients (59) received chemotherapy as well as proton beam therapy. On average, patients were followed-up for 7 years.

Three years after treatment, 12% of patients had serious hearing loss and this rose to 16% at five years.

Patients also displayed problems with processing speed and verbal comprehension, but perceptual reasoning and working memory were not significantly affected.

The researchers found that at five years, more than half (55%) had problems with the neuroendocrine system with growth hormone being the most commonly affected.

However, the study reported no cardiac, pulmonary, or gastrointestinal toxic effects which are common in patients treated with photon radiotherapy.

At three years after treatment, progression-free survival was 83%. At five years, it was 80%.

The authors said: “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.

“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.”

Writing in a linked comment,** Dr David Grosshans of the Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, USA, said: “This study sets a new benchmark for the treatment of paediatric medulloblastoma and alludes to the clinical benefits of advanced radiation therapies.”

* Yock T I, et al. Long-term toxic effects of proton radiotherapy for paediatric medulloblastoma: a phase 2 single-arm study. The Lancet Oncology, 2016. DOI: 10.1016/S1470-2045(15)00167-9

** Grosshans D R, et al. Proton therapy for paediatric medulloblastoma. The Lancet Oncology, 2016. DOI: 10.1016/S1470-2045(15)00217-X

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