title: Pencil Beam Scanning Proton Therapy for Pediatric Parameningeal Rhabdomyosarcomas: Clinical Outcome of Patients Treated at the Paul Scherrer Institute.
abstract: Parameningeal rhabdomyosarcomas (PM-RMSs) represent approximately 25% of all rhabdomyosarcoma (RMS) cases. These tumors are associated with early recurrence and poor prognosis. This study assessed the clinical outcome and late toxicity of pencil beam scanning (PBS) proton therapy (PT) in the treatment of children with PM-RMS.
  
  
  
  Thirty-nine children with PM-RMS received neoadjuvant chemotherapy followed by PBS-PT at the Paul Scherrer Institute, with concomitant chemotherapy. The median age was 5.8 years (range, 1.2-16.1). Due to young age, 25 patients (64%) required general anesthesia during PT. The median time from the start of chemotherapy to PT was 13 weeks (range, 3-23 weeks). Median prescription dose was 54 Gy (relative biologic effectiveness, RBE).
  
  
  
  With a mean follow-up of 41 months (range, 9-106 months), 10 patients failed. The actuarial 5-year progression-free survival (PFS) was 72% (95% CI, 67-94%) and the 5-year overall survival was 73% (95% CI, 69-96%). On univariate analysis, a delay in the initiation of PT (>13 weeks) was a significant detrimental factor for PFS. Three (8%) patients presented with grade 3 radiation-induced toxicity. The estimated actuarial 5-year toxicity ≥grade 3 free survival was 95% (95% CI, 94-96%).
  
  
  
  Our data contribute to the growing body of evidence demonstrating the safety and effectiveness of PT for pediatric patients with PM-RMS. These preliminary results are encouraging and in line with other combined proton-photon and photons series; observed toxicity was acceptable.
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.|Department of Radiation Oncology, Universitätspital Zürich, University of Zurich, Switzerland.|Department of Radiation Oncology, Inselspital, University of Bern, Switzerland.
authors.forename: Damien C
authors.initials: DC
authors.lastname: Weber
authors.affiliation: Department of Radiation Oncology, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Carmen
authors.initials: C
authors.lastname: Ares
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Albertini
authors.affiliation: Department of Anesthesia, University Children's Hospital Zurich, Switzerland.
authors.forename: Martina
authors.initials: M
authors.lastname: Frei-Welte
authors.affiliation: Department of Oncology, University Children's Hospital Zurich, Switzerland.
authors.forename: Felix K
authors.initials: FK
authors.lastname: Niggli
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.
authors.forename: Ralf
authors.initials: R
authors.lastname: Schneider
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland.
authors.forename: Antony J
authors.initials: AJ
authors.lastname: Lomax
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D061766:Proton Therapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted; D012062:Relative Biological Effectiveness; D018233:Rhabdomyosarcoma, Embryonal / Q000401:mortality / Q000532:radiotherapy*; D017211:Treatment Failure
keywords: late toxicity; parameningeal rhabdomyosarcoma; particle radiotherapy; pediatric tumors; pencil beam scanning proton therapy; tumor local control