MRI abnormalities in children following sequential chemotherapy, hyperfractionated accelerated radiotherapy and high-dose thiotepa for high-risk primitive neuroectodermal tumours of the central nervous system

Introduction: Intensive postsurgical therapies have improved survival in children with primitive neuroectodermal tumour, but there is concern that the combination of chemotherapy and radiotherapy may result in a compound injury to normal brain. The purposes of this analysis were to characterise what types of imaging abnormalities occur, identify risk factors and explore how treatment-related changes may be distinguished from tumour. Method: One hundred fifty-three MRI studies in 14 children treated with sequential chemotherapy, hyperfractionated accelerated radiotherapy and high-dose thiotepa were retrospectively analysed at a paediatric national referral centre. Results: We observed 11 episodes of new focal enhancing lesions, 5 of which were transient and judged to be treatment related. In addition, 7/14 (50%) of children demonstrated moderate to severe brain volume loss featuring a leukodystrophy pattern. Conclusion: Treatment-related brain MRI abnormalities occurred frequently in this series with a risk of misdiagnosis as tumour. A proportion of patients suffer generalised white matter injury, which has not been appreciated as a side effect of this particular therapy.