Spot-scanning proton therapy for rhabdomyosarcomas of early childhood. First experiences at PSI

Purpose: To evaluate the feasibility and acute toxicity of spot-scanning proton therapy under deep sedation in young children with rhabdomyosarcomas (RMS). Patients and Methods: Since 2004, children requiring sedation can be admitted for proton therapy at Paul Scherrer Institute (PSI), Villigen, Switzerland. Children under 5 years of age with RMS of the head and the trunk were analyzed. All children were enrolled in a multidisciplinary treatment protocol and prospective, standardized evaluation of side effects was performed. Results: Nine children were included aged 0.9-3.8 years (embryonal RMS in six, and alveolar, undifferentiated or nonclassified in one each). The tumor site was parameningeat (n = 4), orbital (n = 3), head and neck (n = 1), and prostate (n = 1). All children were in IRS group III. Total proton dose was 46-54 CGE (cobalt-gray equivalent). Only the myelotoxicity exceeded grade 3 or 4 (RTOG/EORTC). Conclusion: Proton therapy for RMS in early children is feasible and well tolerated. The prospective standardized evaluation of toxicity and quality of life needs to be continued.