Expected clinical benefits and challenges of particle therapy for paediatric tumours

Abstract

Proton therapy for non-ocular tumours in children is a relatively new development in Europe. Main arguments for proton therapy are the reduced risk for secondary cancers as well as a more precise sparing of organs at risk (OAR). Due to interdisciplinary advances more children survive their childhood cancer and have to deal with late effects of their primary cancer treatment. Children are by about a factor of ten more sensitive to radiation-induced malignancies than adults. Due to a smaller body volume, the scattering is more significant than in the (larger) body of an adult. At the West German Proton Therapy Centre (WPE) 276 children were treated between 06/2013 and 05/2016. 190 patients were 0–10 years, 86 were 11–18 years old. 154 patients needed anaesthesia. The most frequent malignancies treated were CNS tumours (145) and sarcomas (107). Very precise radiation volumes can be achieved e.g. in retroperitoneal malignancies, cranio-spinal axes, ENT and CNS tumours. Sparing of OAR, such as brain stem, hippocampus, pituitary gland, cochlea, chiasma, lacrimal and salivary glands is very important to reduce late side-effects and preserve quality of life. A main challenge of proton therapy remains the prolonged time for treatment planning. Metal or breathing movements in the irradiated volume pose additional challenges and sometimes develop into a pitfall during treatment planning. Similar problems occur, if density changes happen (e.g. growing or shrinking of cysts in the PTV, air inclusions). An adhoc adaption of the treatment plan is not simply arranged, but takes time. Proton therapy for non-ocular tumours in children is a relatively new development in Europe. Main arguments for proton therapy are the reduced risk for secondary cancers as well as a more precise sparing of organs at risk (OAR). Due to interdisciplinary advances more children survive their childhood cancer and have to deal with late effects of their primary cancer treatment. Children are by about a factor of ten more sensitive to radiation-induced malignancies than adults. Due to a smaller body volume, the scattering is more significant than in the (larger) body of an adult. At the West German Proton Therapy Centre (WPE) 276 children were treated between 06/2013 and 05/2016. 190 patients were 0–10 years, 86 were 11–18 years old. 154 patients needed anaesthesia. The most frequent malignancies treated were CNS tumours (145) and sarcomas (107). Very precise radiation volumes can be achieved e.g. in retroperitoneal malignancies, cranio-spinal axes, ENT and CNS tumours. Sparing of OAR, such as brain stem, hippocampus, pituitary gland, cochlea, chiasma, lacrimal and salivary glands is very important to reduce late side-effects and preserve quality of life. A main challenge of proton therapy remains the prolonged time for treatment planning. Metal or breathing movements in the irradiated volume pose additional challenges and sometimes develop into a pitfall during treatment planning. Similar problems occur, if density changes happen (e.g. growing or shrinking of cysts in the PTV, air inclusions). An adhoc adaption of the treatment plan is not simply arranged, but takes time.