title: Population-based study of pseudoprogression after chemoradiotherapy in GBM.
abstract: BACKGROUND
  Chemoradiotherapy followed by monthly temozolomide (TMZ) is the standard of care for patients with glioblastoma multiforme (GBM). Case reports have identified GBM patients who experienced transient radiological deterioration after concurrent chemoradiotherapy which stabilized or resolved after additional cycles of adjuvant TMZ, a phenomenon known as radiographic pseudoprogression. Little is known about the natural history of radiographic pseudoprogression.
  
  
  METHODS
  We retrospectively evaluated the incidence of radiographic pseudoprogression in a population-based cohort of GBM patients and determined its relationship with outcome and MGMT promoter methylation status.
  
  
  RESULTS
  Out of 43 evaluable patients, 25 (58%) exhibited radiographic progression on the first MRI after concurrent treatment. Twenty of these went on to receive adjuvant TMZ, and subsequent investigation demonstrated radiographic pseudoprogression in 10 cases (50%). Median survival (MS) was better in patients with pseudoprogression (MS 14.5 months) compared to those with true radiologic progression (MS 9.1 months, p=0.025). The MS of patients with pseudoprogression was similar to those who stabilized/responded during concurrent treatment (p=0.31). Neither the extent of the initial resection nor dexamethasone dosing was associated with pseudoprogression.
  
  
  CONCLUSIONS
  These data suggest that physicians should continue adjuvant TMZ in GBM patients when early MRI scans show evidence of progression following concurrent chemoradiotherapy, as up to 50% of these patients will experience radiologic stability or improvement in subsequent treatment cycles.
authors.affiliation: Department of Oncology, Tom Baker Cancer Centre, Alberta Cancer Board, Department of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada.
authors.forename: Gloria B
authors.initials: GB
authors.lastname: Roldán
authors.forename: James N
authors.initials: JN
authors.lastname: Scott
authors.forename: John B
authors.initials: JB
authors.lastname: McIntyre
authors.forename: Marisa
authors.initials: M
authors.lastname: Dharmawardene
authors.forename: Paula A
authors.initials: PA
authors.lastname: de Robles
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Magliocco
authors.forename: Elizabeth S Y
authors.initials: ES
authors.lastname: Yan
authors.forename: Ian F
authors.initials: IF
authors.lastname: Parney
authors.forename: Peter A
authors.initials: PA
authors.lastname: Forsyth
authors.forename: J Gregory
authors.initials: JG
authors.lastname: Cairncross
authors.forename: Mark G
authors.initials: MG
authors.lastname: Hamilton
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Easaw
mesh_terms: D000328:Adult; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000532:radiotherapy*; D015331:Cohort Studies; D003131:Combined Modality Therapy; D018672:Community Health Planning; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D018450:Disease Progression; D005260:Female; D005909:Glioblastoma / Q000188:drug therapy* / Q000401:mortality / Q000532:radiotherapy*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018714:Radiotherapy, Adjuvant / Q000379:methods*; D012189:Retrospective Studies; D016019:Survival Analysis; D000077204:Temozolomide; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003606:Dacarbazine; D000077204:Temozolomide