title: Correlation of local failure with measures of dose insufficiency in the high-dose single-fraction treatment of bony metastases.
abstract: OBJECTIVE
  In the setting of high-dose single-fraction image-guided radiotherapy of spine metastases, the delivered dose is hypothesized to be a significant factor in local control. We investigated the dependence of local control on measures of dose insufficiency.
  
  
  METHODS
  The minimum doses received by the hottest 100%, 98%, and 95% (D(min), D(98), and D(95)) of the gross target volume (GTV) were computed for 91 consecutively treated lesions observed in 79 patients. Prescribed doses of 18-24 Gy were delivered in a single fraction. The spinal cord and cauda equina were constrained to a maximum dose of 12-14 Gy and 16 Gy, respectively. A rank-sum test was used to assess the differences between radiographic local failure and local control.
  
  
  RESULTS
  With a median follow-up of 18 months, seven local failures have occurred. The distributions of GTV D(min), D(98), and D(95) for treatments resulting in local failure were found to be statistically different from the corresponding distributions of the patient group as a whole. Taking no account of histology, p values calculated for D(min), D(98), and D(95) were 0.004, 0.012, and 0.031, respectively. No correlations between local failure and target volume or between local failure and anatomic location were found.
  
  
  CONCLUSIONS
  The results indicate that D(min), D(98), and D(95) may be important risk factors for local failure. No local failures in any histology were observed when D(min) was >15 Gy, suggesting that this metric may be an important predictor of local control.
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. lovelocm@mskcc.org
authors.forename: D Michael
authors.initials: DM
authors.lastname: Lovelock
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Andrew
authors.initials: A
authors.lastname: Jackson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Keam
authors.forename: Justin
authors.initials: J
authors.lastname: Bekelman
authors.forename: Mark
authors.initials: M
authors.lastname: Bilsky
authors.forename: Eric
authors.initials: E
authors.lastname: Lis
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000556:secondary; D018450:Disease Progression; D006801:Humans; D010384:Pelvic Bones / Q000000981:diagnostic imaging; D019736:Prostheses and Implants; D011859:Radiography; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000556:secondary; D017211:Treatment Failure; D047368:Tumor Burden