Late bone and soft tissue sequelae of childhood radiotherapy. Relevance of treatment age and radiation dose in 146 children treated between 1970 and 1997.

PURPOSE: The present retrospective study was initiated to characterize the effect of oncological treatments in children and adolescents on bone and soft tissues, and to assess their dependence on radiation dose and age at exposure. PATIENTS AND METHODS: The study included 146 patients treated between 1970 and 1997. All patients received external beam radiotherapy to the trunk or extremities, but no cranial irradiation. Median age at treatment was 8.8 years. Patients were screened at 18 years (median time interval since treatment 9.2 years, range 0.9-17.7 years) for pathological changes in the skeletal system and soft tissues (scoliosis, kyphosis, bony hypoplasia, soft tissue defects, asymmetries), which were classified as minor/moderate (grade 1) or substantial (grade 2).
RESULTS: Pathological findings were recorded in 75/146 patients (51 %). These were scored as minor in 44 (59 %) and substantial in 31 patients (41 %). Most pathological changes occurred in children treated under the age of 6 years. At 6 years and older, only doses > 35 Gy caused an effect, and no substantial changes were seen for treatment ages exceeding 12 years. Significant effects of radiation dose and age at exposure were observed for kyphoscoliosis (with vertebral body dose gradients < 35 Gy), hypoplasia and soft tissue defects and asymmetrical growth.
CONCLUSION: Tolerance doses of 20 Gy need to be respected for growing bone, particularly in children treated under the age of 6 years. The late treatment sequelae analysed in the present study are largely avoided with the use of current therapeutic protocols. However, the systematic evaluation, documentation and continuous analysis of adverse events in paediatric oncology remains essential, as does the evaluation of novel radio(chemo)therapeutic approaches.