Why are not all paediatric cancer patients treated with protons? A population-based report from Sweden, 2016-2023.

Background: In 2015, a proton therapy (PT) facility was established in Sweden with one aim being to ensure access for all children expected to benefit from PT. Despite potential dosimetric advantages and full subsidisation, PT is not always selected. This study explores reasons for choosing alternative radiotherapy (RT) modalities in a paediatric population.

Material and methods: RT courses delivered to patients ≤ 18 years during 2016-2023 were identified from a national registry. Medical records were retrospectively reviewed to identify reasons for not selecting PT.

Results: Only 34% (n = 275) of all courses identified were delivered with PT. Of the remaining 66% (n = 544), 90% were photon RT, 9% combined PT and photon RT, and 1% electron RT. Among photon RT courses, 97% were delivered with conventional external beam radiotherapy (EBRT), 2% with stereotactic radiotherapy (SRT), and 1% with brachytherapy. The most common reason for choosing photons was non-curative intent (35%), followed by equal or superior expected outcome compared to PT (23%), total body irradiation (TBI) (15%), and uncertainties due to air, organ motion, or metal in field (15%). Dosimetric comparison led to the selection of a favourable or equal photon plan in 8%. Logistical, social, and technical reasons constituted 4%.

Conclusion: While PT can reduce radiation exposure to healthy tissues, particularly important in children, clinical, logistical, and technical factors often necessitate alternative RT modalities. This study highlights the importance of individualised RT planning and multidisciplinary collaboration to balance medical, technical, and practical considerations to ensure optimal treatment approach in every child.