**12. Radiotherapy**

Radiotherapy plays an important role in the management of pediatric brain tumours. It can be used either as adjuvant treatment in case of resectable tumours or as a definitive management option in case of unresectable tumours [22].

The most common long term side effect of radiotherapy in pediatric age group is neurocognitive dysfunction and upto 20–60% patients suffer from neurocognitive deficit as a long term sequelae of radiotherapy [23]. Sophisticated radiotherapy techniques are warranted for to avoid future negative impacts of radiation on pediatric brain development.

Use of better immobilization and more suitable imaging techniques like highresolution brain imaging with computed tomography (CT) and magnetic resonance imaging (MRI) to accurately define the tumour limits and precisely assess the normal brain structures has greatly improved the degree of efficacy achieved by radiotherapy without increasing the side effects [24].

Technological advancements like use of conformal radiotherapy allows high radiation dose distributions within targeted tissues while simultaneously attempting to reduce dose to surrounding normal tissues. Conformal radiotherapy can be accomplished through a variety of techniques, including intensity-modulated radiotherapy (IMRT), stereotactic radiotherapy and proton beam therapy.

IMRT has shown promise in the treatment of a number of disease sites and is now being investigated in the use of pediatric tumors to reduce long-term toxicity. Stereotactic technique has the ability to reduce the treatment volume as it delivers highly conformal radiation to brain tumours and minimum dose to surrounding brain tissue. It can be delivered as stereotactic radiosurgery in which the entire dose is delivered as a single fraction or as fractionated stereotactic radiotherapy (FSRT) in which the treatment is delivered over weeks with multiple daily fractions. Only small margins of several millimeters are used for brain tumors, greatly reducing the volume of normal brain parenchyma receiving high doses of radiation.
