Spinal deformity after intra-operative radiotherapy for paediatric patients

The purpose of this study was to clarify the incidence and characteristics of late-onset complications of the spine in children who underwent intra-operative radiation therapy (IORT) for common paediatric malignant tumours. 12 children with more than 4 years of follow-up after IORT were included and, in 11 of these, thoracic and/or lumbar spines were irradiated. To compare doses of irradiation to the spine with the resulting deformities, dose simulations of IORT were carried out on two selected cases using a radiation treatment planning system with a pencil-beam algorithm. The mean follow-up period was 135 months (range, 53-234 months). Radiographic reviews found spinal deformity in six patients. Only one patient was symptomatic and the spinal deformity was severe (Grade 3), whereas spinal deformity was mild in the remaining five patients without clinical symptoms (Grade 1). In all of the six patients, anterior wedge-shaped deformity was dominant, and scoliosis was found in only two patients. In one particular case with nephrectomy, irradiation had penetrated much deeper than usual at the site of nephrectomy, and dose distribution was asymmetric, causing clinically significant spinal deformity with scoliosis. In conclusion, specific deformities of the spine observed after IORT can be explained on the basis of dose distribution of the electron beam to the spine.