title: Calvarial and skull base metastases: expanding the clinical utility of Gamma Knife surgery.
abstract: OBJECTIVE
  Traditionally, the treatment of choice for patients with metastases to the calvaria or skull base has been conventional radiation therapy. Because patients with systemic malignancies are also at risk for intracranial metastases, the utility of Gamma Knife surgery (GKS) for these patients has been explored to reduce excess radiation exposure to the perilesional brain parenchyma. The purpose of this study was to report the efficacy of GKS for the treatment of calvarial metastases and skull base lesions.
  
  
  METHODS
  The authors performed a retrospective chart review of 21 patients with at least 1 calvarial or skull base metastatic lesion treated with GKS during 2001-2013. For 7 calvarial lesions, a novel technique, in which a bolus was placed over the treatment site, was used. For determination of local control or disease progression, radiation therapy data were examined and posttreatment MR images and oncology records were reviewed. Survival times from the date of procedure were estimated by using Kaplan-Meier analyses.
  
  
  RESULTS
  The median patient age at treatment was 57 years (range 29-84 years). A total of 19 (90%) patients received treatment for single lesions, 1 patient received treatment for 3 lesions, and 1 patient received treatment for 4 lesions. The most common primary tumor was breast cancer (24% of patients). Per lesion, the median clinical and radiographic follow-up times were 10.3 months (range 0-71.9 months) and 7.1 months (range 0-61.3 months), respectively. Of the 26 lesions analyzed, 14 (54%) were located in calvarial bones and 12 (46%) were located in the skull base. The median lesion volume was 5.3 cm(3) (range 0.3-55.6 cm(3)), and the median prescription margin dose was 15 Gy (range 13-24 Gy). The median overall survival time for all patients was 35.9 months, and the 1-year local control rate was 88.9% (95% CI 74.4%-100%). Local control rates did not differ between lesions treated with the bolus technique and those treated with traditional methods or between calvarial lesions and skull base lesions (p > 0.05). Of the 3 patients for whom local treatment failed, 1 patient received no further treatment and 2 patients responded to salvage chemotherapy. Subsequent brain parenchymal metastases developed in 2 patients, who then underwent GKS.
  
  
  CONCLUSIONS
  GKS is an effective treatment modality for patients with metastases to the calvarial bones or skull base. For patients with superficial calvarial lesions, a novel approach with bolus application resulted in excellent rates of local control. GKS provides an effective therapeutic alternative to conventional radiation therapy and should be considered for patients at risk for calvarial metastases and brain parenchymal metastases.
authors.affiliation: Departments of 1 Radiation Oncology and.
authors.forename: Rupesh
authors.initials: R
authors.lastname: Kotecha
authors.forename: Lilyana
authors.initials: L
authors.lastname: Angelov
authors.forename: Gene H
authors.initials: GH
authors.lastname: Barnett
authors.forename: Chandana A
authors.initials: CA
authors.lastname: Reddy
authors.forename: John H
authors.initials: JH
authors.lastname: Suh
authors.forename: Erin S
authors.initials: ES
authors.lastname: Murphy
authors.forename: Gennady
authors.initials: G
authors.lastname: Neyman
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Chao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000473:pathology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery; D003131:Combined Modality Therapy; D016371:Cranial Irradiation / Q000379:methods; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D017567:Karnofsky Performance Status; D007680:Kidney Neoplasms / Q000473:pathology; D008175:Lung Neoplasms / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D016634:Radiosurgery / Q000379:methods*; D011878:Radiotherapy / Q000379:methods; D012189:Retrospective Studies; D012307:Risk Factors; D012886:Skull; D019292:Skull Base Neoplasms / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery
keywords: GKS = Gamma Knife surgery; Gamma Knife surgery; RTOG = Radiation Therapy Oncology Group; calvarial; metastasis; skull; stereotactic radiosurgery