title: Long term outcomes of patients with skull-base low-grade chondrosarcoma and chordoma patients treated with pencil beam scanning proton therapy.
abstract: To evaluate the long term tumor control and toxicity of skull base tumors treated with pencil beam scanning proton therapy (PT).
  
  
  
  PT was delivered to 151 (68%) and 71 (32%) chordoma and chondrosarcoma (ChSa) patients, respectively. Mean age of patients was 40.8±18.4years and the male to female ratio was 0.53. The postoperative tumor was abutting the brainstem or optic apparatus in 71 (32.0%) patients. The postoperative mean gross tumor volume (GTV) was 35.7±29.1cm(3). The delivered mean PT dose was 72.5±2.2GyRBE.
  
  
  
  After a mean follow-up of 50 (range, 4-176) months, 35 local (15.8%) failures were observed between 10.9 and 85.4months. The estimated 7-year LC rate for chordoma (70.9%; CI95% 61.5-81.8) was significantly lower compared to the LC rate for ChSa patients (93.6%; 95%CI 87.8-99.9; P=0.014). The estimated 7-year distant metastasis-free- and overall survival rate was 91.6% (95%CI 91.6-98.6) and 81.7% (95%CI 74.7-89.5), respectively. On multivariate analysis, optic apparatus and/or brainstem compression, histology and GTV were independent prognostic factors for LC and OS. The 7-year high grade toxicity-free survival was 87.2 (95%CI 82.4-92.3).
  
  
  
  PBS PT is an effective treatment for skull base tumors with acceptable late toxicity. Optic apparatus and/or brainstem compression, histology and GTV allow independent prediction of the risk of local failure and death in skull base tumor patients.
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland; University of Bern, Switzerland; University of Zürich, Switzerland. Electronic address: damiencharles.weber@uzh.ch.
authors.forename: Damien C
authors.initials: DC
authors.lastname: Weber
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Malyapa
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Albertini
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bolsi
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kliebsch
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Walser
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Alessia
authors.initials: A
authors.lastname: Pica
authors.affiliation: Unité d'Epidemiologie Clinique, Hôpitaux Universitaire de Genève, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Combescure
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland; ETH, Zürich, Switzerland.
authors.forename: Antony J
authors.initials: AJ
authors.lastname: Lomax
authors.affiliation: Center for Proton Therapy, Paul Scherrer Institute, Switzerland.
authors.forename: Ralf
authors.initials: R
authors.lastname: Schneider
mesh_terms: D000328:Adult; D000368:Aged; D002813:Chondrosarcoma / Q000532:radiotherapy*; D002817:Chordoma / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy / Q000379:methods*; D019292:Skull Base Neoplasms / Q000532:radiotherapy*; D016896:Treatment Outcome; D055815:Young Adult
keywords: Chondrosarcoma; Chordoma; Pencil beam scanning; Proton therapy; Skull base tumors