Paediatric proton therapy

Abstract

Proton beam therapy is a highly conformal form of radiation therapy, which currently represents an important therapeutic component in multidisciplinary management in paediatric oncology. The precise adjustability of protons results in a reduction of radiation-related long-term side-effects and secondary malignancy induction, which is of particular importance for the quality of life. Proton irradiation has been shown to offer significant advantages over conventional photon-based radiotherapy, although the biological effectiveness of both irradiation modalities is comparable. This review evaluates current data from clinical and dosimetric studies on the treatment of tumours of the central nervous system, soft tissue and bone sarcomas of the head and neck region, paraspinal or pelvic region, and retinoblastoma. To date, the clinical results of irradiating childhood tumours with high-precision proton therapy are promising both with regard to tumour cure and the reduction of adverse events. Modern proton therapy techniques such as pencil beam scanning and intensity modulation are increasingly established modern facilities. However, further investigations with larger patient cohorts and longer follow-up periods are required, in order to be able to have clear evidence on clinical benefits.

Figure 1.

Positioning and immobilization of a child with an anaplastic ependymoma treated with pencil beam scanning proton therapy.

Figure 2.

Evidence of paediatric PBT. All restrospective and prospective studies published in PubMed in the last ten years (2009–2019) on paediatric proton therapy are presented (a) with regard to mean number of patients and median FU period (b); FU (mo), follow up in months; CNS, central nervous system; FU, follow-up; PBT, proton beam therapy.

Figure 3.

Pencil beam scanning proton therapy plan (sagittal (a) and axial (b) view) for a child with an ependymoma (RayStation^®). Red area: covered by 95% isodose line, yellow: 90% isodose, light blue: 50% isodose, dark blue: 20% isodose.

Figure 4.

Pencil beam scanning proton therapy plan (sagittal (a), axial (b) and coronal (c) view) for a 11 year old child with an Ewing sarcoma of the thoracic (RayStation^®). Red area: covered by 95% isodose line, yellow: 90% isodose, light green: 80% isodose, dark green: 60% isodose, light blue: 40% isodose, dark blue: 20% isodose.