title: Challenges in linear accelerator radiotherapy for chordomas and chondrosarcomas of the skull base: focus on complications.
abstract: OBJECTIVE
  Intracranial chordomas and chondrosarcomas are histologically low-grade, locally invasive tumors that infiltrate the skull base. Currently, consensus therapy includes surgical resection and adjuvant radiotherapy. Radiation delivery is typically limited by the proximity of these tumors to critical skull base structures.
  
  
  METHODS
  This is a retrospective review of 13 cases of chordomas and 2 cases of chondroid chondrosarcomas of the skull based treated with linear accelerator stereotactic radiotherapy (SRT, n = 10) or stereotactic radiosurgery (SRS, n = 5). The average time to the most recent follow-up visit was 4.5 years. The tumor characteristics, treatment details, and outcomes were recorded. Each radiation plan was reviewed, and the dosage received by the brainstem, optic apparatus, and pituitary was calculated.
  
  
  RESULTS
  Of the 10 patients treated with SRT, 6 were found to have unchanged or decreased tumor size as determined from radiographic follow-up. Of the 5 patients treated with SRS, 3 were found to have stable or unchanged tumors at follow-up. The complications included 1 SRT patient who developed endocrinopathy, 2 patients (1 treated with SRS and the other with SRT), who developed cranial neuropathy, and 1 SRS patient who developed visual deficits. Additionally, 1 patient who received both SRS and SRT within 2 years for recurrence experienced transient medial temporal lobe radiation changes that resolved.
  
  
  CONCLUSIONS
  Where proton beam therapy is unavailable, linear accelerator-based SRT or radiosurgery remains a safe option for adjuvant therapy of chordomas and chondrosarcomas of the skull base. The exposure of the optic apparatus, pituitary stalk, and brainstem must be considered during planning to minimize complications. If the optic apparatus is included in the 80% isodose line, it might be best to fractionate therapy. Exposure of the pituitary stalk should be kept to <30 Gy to minimize endocrine dysfunction. Brainstem exposure should be limited to <60 Gy in fractions.
authors.affiliation: Division of Stereotactic and Functional Neurosurgery, Department of Neurosurgery, University of California, Los Angeles, David Geffen School of Medicine, Los Angeles, CA 90095-7039, USA. jhauptman@mednet.ucla.edu
authors.forename: Jason S
authors.initials: JS
authors.lastname: Hauptman
authors.forename: Garni
authors.initials: G
authors.lastname: Barkhoudarian
authors.forename: Michael
authors.initials: M
authors.lastname: Safaee
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gorgulho
authors.forename: Steven
authors.initials: S
authors.lastname: Tenn
authors.forename: Nzhde
authors.initials: N
authors.lastname: Agazaryan
authors.forename: Michael
authors.initials: M
authors.lastname: Selch
authors.forename: Antonio A F
authors.initials: AA
authors.lastname: De Salles
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology / Q000601:surgery*; D001933:Brain Stem / Q000528:radiation effects; D002813:Chondrosarcoma / Q000473:pathology / Q000601:surgery*; D002817:Chordoma / Q000473:pathology / Q000601:surgery*; D005123:Eye / Q000528:radiation effects; D005158:Facial Paralysis / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use; D010902:Pituitary Gland / Q000528:radiation effects; D011832:Radiation Injuries / Q000150:complications*; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012189:Retrospective Studies; D019292:Skull Base Neoplasms / Q000473:pathology / Q000601:surgery*; D047368:Tumor Burden / Q000528:radiation effects; D014786:Vision Disorders / Q000209:etiology