Paediatrics: Radiotherapy

Radiotherapy

In the use of ionizing radiation to kill cancer cells, dose and fractiona-tion (number of treatments to deliver a total dose) vary according to the nature of the tumour and tolerance of the tissue.

Strategies to increase therapeutic success include:

·Conformal radiotherapy: matching beam to 3D shape of target and so sparing surrounding tissue.

·Hyperfractionation and acceleration.

·Targeted radiotherapy with specific isotopes, e.g. I¹³¹MIBG for neuroblastoma,

·Radiosurgery (high dose single fraction), brachytherapy (direct application of radionuclides to tumour). Protons (reduced dose to non-target tissues): currently limited availability in paediatrics.

Indications

·Selected cases of Hodgkin’s disease, neuroblastoma, Wilms’ tumour, soft tissue and ESs, most subgroups of CNS tumours.

·Limited benefit in OS, extracranial GCTs, NHL.

·In leukaemia limited to treatment of CNS and testicular disease and to conditioning for BMT.

·Symptom control in palliative care, e.g. bony metastases, spinal cord compression.

Preparation for radiotherapy

·Planning, by combination of CT and MRI scanning.

·Immobilization using masks/shells, tattoos as markers; sedation or general anaesthesia for youngest children.

·Protection of surrounding tissues, e.g. gonads, using lead shields.

·Play therapists have a central role in this process.

Side-effects

·Acute effects include nausea and vomiting, cutaneous erythema and desquamation, diarrhoea, myelosuppression, pneumonitis, hepatitis. Toxicity is potentiated by actinomycin D or anthracyclines.

·Late effects on growth, CNS, heart, lungs, kidneys, liver.