Abstract
Simple SummaryRadiotherapy has a key role in treatment of pediatric cancer and has greatly improved survival in recent years. However, vertebrae are often included in the irradiated area, and this may affect growth after treatment. In this study, we examined the relationship of the dose of proton beam therapy with subsequent growth of 353 vertebral bodies in 23 children (10 boys, 13 girls) with a median age at treatment of 4 years old and a median observation period of 13.9 months. Most importantly, we found that the growth rate of vertebral bodies decreased even at a low proton beam therapy dose, which indicates the need for careful planning of the irradiation area in this patient population. Growth inhibition was clearly dose-dependent, and proton beam therapy had the same growth inhibitory effect as photon radiotherapy, at least within the irradiated field.Impairment of bone growth after radiotherapy for pediatric bone cancer is a well-known adverse event. However, there is limited understanding of the relationship between bone growth and irradiation dose. In this study, we retrospectively analyzed bone growth impairment after proton beam therapy for pediatric cancer. A total of 353 vertebral bodies in 23 patients under 12 years old who received proton beam therapy were evaluated. Compared to the non-irradiated vertebral body growth rate, the irradiated vertebral body rate (%/year) was significantly lower: 77.2%, 57.6%, 40.8%, 26.4%, and 14.1% at 10, 20, 30, 40, and 50 Gy (RBE) irradiation, respectively. In multivariate analysis, radiation dose was the only factor correlated with vertebral body growth. Age, gender, and vertebral body site were not significant factors. These results suggest that the growth rate of the vertebral body is dose-dependent and decreases even at a low irradiated dose. This is the first report to show that proton beam therapy has the same growth inhibitory effect as photon radiotherapy within the irradiated field.
Highlights
Radiotherapy plays an important role in multidisciplinary treatment for various childhood tumors
Vertebrae are often included in the irradiation field in radiotherapy for a pediatric tumor, especially for tumors near the spine, such as neuroblastoma or nephroblastoma, and patients who are at risk of meningeal dissemination such as medulloblastoma or ependymoma may receive craniospinal irradiation (CSI) [3]
Vega et al performed a cost-effective analysis from a societal perspective using a Monte Carlo simulation model [24]. They came to a similar conclusion that proton therapy is a cost-effective strategy for the management of pediatric patients with medulloblastoma compared with standard of care photon therapy
Summary
Radiotherapy plays an important role in multidisciplinary treatment for various childhood tumors. Proton beam therapy is likely to reduce the risks of growth and development disorders, endocrine dysfunction, reduced fertility, and secondary cancer in children. This is because of its characteristic distribution of a decreased dose and volume in normal organs, and maintenance of efficacy against the tumor [7,8,9]. Sethi et al evaluated 86 pediatric patients with retinoblastoma who were treated with proton beam therapy (n = 55) or photon radiotherapy (n = 31) They found that the 10-year cumulative incidence of radiotherapyinduced or in-field secondary malignancies was significantly different between radiation modalities (proton vs photon: 0% vs 14%; p = 0.015). We examined quantitative relationships between dose and vertebral growth changes after proton beam therapy
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