小児腫瘍に対する放射線治療

Radiation therapy for pediatric solid tumors

小児腫瘍に対する放射線治療は，集学的治療の重要な柱であり，病期やリスク分類に基づいた適切な適応と線量設定が求められる^1）。本稿では，神経芽腫（神経芽細胞腫），横紋筋肉腫，Ewing肉腫，Wilms腫瘍，肝芽腫・骨肉腫など主要小児腫瘍に対する放射線治療の役割と最新の照射指針，さらに陽子線治療を含めた晩期毒性低減の取り組みについて概説する。

Radiotherapy plays a pivotal role in the multidisciplinary management of pediatric malignancies, including both solid tumors and hematologic cancers such as leukemia. This article outlines the current principles and clinical evidence for radiotherapy in major pediatric cancers, including neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, Wilms tumor, hepatoblastoma, and osteosarcoma. For each disease entity, we summarize key aspects of risk stratification, treatment planning, and dose prescriptions based on international protocols such as COG, INRG, and JWiTS/SIOP guidelines. The indications for radiotherapy are discussed in the context of surgery and chemotherapy, emphasizing appropriate target volume definition（GTV, CTV, PTV）and optimal timing relative to systemic therapy. Special attention is given to late toxicities, including growth disturbances, endocrine dysfunction, and the risk of secondary malignancies, which are of particular concern in childhood cancer survivors. Proton beam therapy（PBT）offers a distinct advantage by reducing radiation exposure to surrounding normal tissues, thereby mitigating long-term adverse effects such as neurocognitive decline, ototoxicity, and radiation-induced secondary cancers. Recent meta-analyses from the Tsukuba Review Project have demonstrated comparable tumor control between PBT and conventional X-ray radiotherapy（XRT）across major pediatric cancers, with potential benefits in toxicity reduction. Future challenges include the accumulation of long-term follow-up data, particularly regarding late effects and secondary malignancy risk, as well as the evaluation of combined-modality treatment with high-intensity chemotherapy. International collaborative registries and prospective studies are essential to further refine treatment guidelines and optimize outcomes for children with cancer.