title: Pattern of failure after limited margin radiotherapy and temozolomide for glioblastoma.
abstract: OBJECTIVE
  To evaluate the pattern of failure after limited margin radiotherapy for glioblastoma.
  
  
  METHODS
  We analyzed 62 consecutive patients with newly diagnosed glioblastoma treated between 2006 and 2008 with standard fractionation to a total dose of 60 Gy with concurrent temozolomide (97%) or arsenic trioxide (3%). The initial clinical target volume included postoperative T2 abnormality with a median margin of 0.7 cm. The boost clinical target volume included residual T1-enhancing tumor and resection cavity with a median margin of 0.5 cm. Planning target volumes added a 0.3- or 0.5-cm margin to clinical target volumes. The total boost planning target volume (PTV(boost)) margin was 1cm or less in 92% of patients. The volume of recurrent tumor (new T1 enhancement) was categorized by the percent within the 60-Gy isodose line as central (>95%), infield (81-95%), marginal (20-80%), or distant (<20%). For comparison, an initial planning target volume with a 2-cm margin and PTV(boost) with a 2.5-cm margin were created for each patient.
  
  
  RESULTS
  With a median follow-up of 12 months, radiographic tumor progression developed in 43 of 62 patients. Imaging was available for analysis in 41: 38 (93%) had central or infield failure, 2 (5%) had marginal failure, and 1 (2%) had distant failure relative to the 60-Gy isodose line. The treated PTV(boost) (median, 140 cm(3)) was, on average, 70% less than the PTV(boost) with a 2.5-cm margin (median, 477 cm(3)) (p < 0.001).
  
  
  CONCLUSIONS
  A PTV(boost) margin of 1cm or less did not appear to increase the risk of marginal and/or distant tumor failures compared with other published series. With careful radiation planning and delivery, it appears that treatment margins for glioblastoma can be reduced.
authors.affiliation: Department of Radiation Oncology, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: Mark W
authors.initials: MW
authors.lastname: McDonald
authors.forename: Hui-Kuo G
authors.initials: HK
authors.lastname: Shu
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Curran
authors.forename: Ian R
authors.initials: IR
authors.lastname: Crocker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy / Q000379:methods; D003606:Dacarbazine / Q000008:administration & dosage / Q000031:analogs & derivatives; D018450:Disease Progression; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D005909:Glioblastoma / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D009367:Neoplasm Staging; D010087:Oxides / Q000008:administration & dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D000077204:Temozolomide; D014057:Tomography, X-Ray Computed; D017211:Treatment Failure; D047368:Tumor Burden; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D003606:Dacarbazine; D000077237:Arsenic Trioxide; D000077204:Temozolomide