Pencil beam radiotherapy may help preserve memory in children with brain tumours

Chloe Kent 29 April 2019 (Last Updated April 29th, 2019 17:00)

A study presented at the ESTRO 38 conference has indicated that a type of radiotherapy called pencil beam scanning proton therapy offers the best hope for preserving cognitive functions in children with craniopharyngioma brain tumours.

Pencil beam radiotherapy may help preserve memory in children with brain tumours
Pencil beam scanning proton therapy delivers an extremely precise dose of radiotherapy via a very narrow proton beam. Credit: Pete Linforth

A study presented at the ESTRO 38 conference in Milan, Italy, has indicated that a type of radiotherapy called pencil beam scanning proton therapy (PBS) offers the best hope for preserving cognitive functions in children with craniopharyngioma brain tumours.

PBS delivers an extremely precise dose of radiotherapy via a very narrow proton beam. In craniopharyngioma patients, whose tumours are embedded deep in the centre of the brain, PBS can be used to deliver a relatively low dose of radiation to the temporal lobes and hippocampus.

As these two areas of the brain are heavily associated with memory function, reducing their radiation exposure may help to preserve a patient’s recall abilities following treatment.

Three types of radiotherapy were assessed during in the study: volumetric modulated arc therapy (VMAT), double scattering proton therapy (DSPT) and PBS. Their usage was monitored by researchers as Aarhus University Hospital, Denmark, in ten children diagnosed with craniopharyngioma tumours.

VMAT is a type of intensity modulated radiotherapy (IMRT), which allows the radiation dose to be shaped to the tumour by modulating the intensity of the radiation beam. Both DSPT and PBS are types of proton therapy, which is better at targeting a tumour more specifically while sparing the surrounding tissues, using high-energy beams to treat tumours which can be directed with more precision than other forms of radiotherapy.

The researchers used previous research on the impact of radiation on children’s brains, including in the temporal lobes and hippocampus, to select 30 structures in the patient’s brains to study.

They used CT and MRI scans to precisely locate the structures in each of these children’s brains, then compared the three treatment plans for each child to see which type was better for sparing those 30 structures from radiation. The dosage to each structure was categorised as low, medium or high.

They found that doses to the temporal lobe were lower with PBS treatment than in both VMAT and DSPT treatment. Data from the study allowed them to predict that proton therapies, and particularly PBS treatment, would result in less impairment in children’s memory function when using radiotherapy to treat craniopharyngioma.

Aarhus University Hospital PhD student Laura Toussaint said: “We have looked at three types of radiotherapy, which all aim to successfully treat brain tumours while doing as little damage to children’s brains as possible. What we found was that pencil beam scanning proton therapy seems to be by far the best at avoiding parts of the brain that are important in children’s memory. The next step would be to confirm this finding with clinical research in patients.

“The use of proton therapy has been expanding rapidly over the last decade and is becoming more and more available for cancer patients, especially for children. This also means that more research can take place.”