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An analysis of muscle growth after proton beam therapy for pediatric cancer
Hazuki Nitta1, Masashi Mizumoto1, Yinuo Li1
1Department of Radiation Oncology, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8575, Japan.
Insights
Proton beam therapy (PBT) significantly reduces muscle growth in pediatric patients, with younger children experiencing more growth retardation. Long-term follow-up is crucial for assessing this effect.
Area of Science:
- Pediatric Oncology
- Radiation Oncology
- Developmental Biology
Background:
- Radiotherapy in pediatric patients can cause growth and development retardation.
- Proton beam therapy (PBT) is an advanced radiation technique used in children.
- Understanding PBT's specific effects on musculoskeletal development is essential.
Purpose of the Study:
- To evaluate the impact of PBT on muscle growth in pediatric patients.
- To compare muscle growth between irradiated and non-irradiated (contralateral) sides.
- To investigate correlations between muscle growth, irradiation dose, and patient age.
Main Methods:
- Retrospective analysis of 17 pediatric patients (age ≤ 5 years) who received PBT.
- Measurement of muscle thickness on CT or MRI scans before and after PBT.
- Comparison of muscle growth rates (mm/year) between irradiated and contralateral muscles.
Main Results:
- Significantly reduced muscle growth observed on the irradiated side (0.24 mm/year) compared to the contralateral side (1.19 mm/year) (P=0.001).
- Younger patients exhibited greater muscle growth.
- Higher irradiation doses (>50 Gy RBE) were associated with minimal muscle growth, though dose correlation was not statistically significant.
Conclusions:
- Proton beam therapy negatively affects muscle growth in pediatric patients.
- Muscle growth retardation is a significant long-term effect requiring monitoring.
- Age at treatment initiation is a factor influencing muscle growth post-PBT.
Abstract:
Retardation of growth and development is a well-known late effect after radiotherapy for pediatric patients. The goal of the study was to examine the effect of proton beam therapy (PBT) on the growth of muscles included in the irradiated area. The subjects were 17 pediatric patients (age ≤ 5 years) who received PBT with a treatment field including a muscle on only one side out of a pair of symmetrical bilateral muscles and had imaging evaluations for at least 1 year after PBT. The thicknesses of the irradiated and non-irradiated (contralateral) muscles were measured retrospectively on CT or MRI axial images collected before and after PBT. The change of thickness divided by the period (years) for each muscle was compared between the irradiated and contralateral sides. Correlations of muscle growth with irradiation dose and age at the start of treatment were also evaluated. The median observation period was 39.2 months. The measurement sites included the erector spinae (n = 9), gluteus maximus (n = 5) and rhomboids + trapezius (n = 3) muscles. The average changes in muscle thickness were 0.24 mm/year on the irradiated side and 1.19 mm/year on the contralateral side, showing significantly reduced growth on the irradiated side (P = 0.001). Younger patients had greater muscle growth. Irradiation dose was not significant, but muscle growth tended to decrease as the dose increased, and muscles irradiated at >50 Gy (RBE) showed little growth. These results show that muscle growth is affected by PBT and that long-term follow-up is needed to evaluate muscle growth retardation.
