title: Endogenous markers of two separate hypoxia response pathways (hypoxia inducible factor 2 alpha and carbonic anhydrase 9) are associated with radiotherapy failure in head and neck cancer patients recruited in the CHART randomized trial.
abstract: OBJECTIVE
  Randomized controlled trials have generally shown a benefit from accelerated radiotherapy in head and neck squamous cell carcinoma (HNSCC). However, the large randomized United Kingdom trial CHART (Continuous Hyperfractionated Accelerated Radiotherapy) failed to show a benefit of strongly accelerated over standard radiotherapy (RT) in 918 patients with HNSCC. In this study, we investigated the impact of tumor hypoxia on the outcome of HNSCC patients in the CHART trial. There are two distinct hypoxia inducible factors (HIFs) that control different gene response pathways and we assessed them both with endogenous markers of hypoxia, hypoxia inducible factor HIF-2 alpha (HIF-2) and carbonic anhydrase CA9, an indicator of HIF-1 alpha (HIF-1) function.
  
  
  METHODS
  Tissue from pre-RT biopsies performed in 198 of 918 patients recruited was analyzed for the immunohistochemical expression of HIF-2 and CA9.
  
  
  RESULTS
  A significant association of high HIF2 and of high CA9 reactivity with poor locoregional control (P < .0001 and P = .0002, respectively) and poor survival (P = .0004 and 0.002, respectively) was noted. In multivariate analysis, HIF-2 and CA9 maintained their independent prognostic significance. Coexpression of both pathways had an additive effect, supporting their independent role. The uni-directional hypothesis, that a benefit from randomization to CHART should be seen in the nonhypoxic tumors, was supported by the data (one-tailed P = .04).
  
  
  CONCLUSIONS
  Expression of endogenous markers of hypoxia for the HIF-1 and HIF-2 pathway is strongly associated with radiotherapy failure. Using immunohistochemical methods it is possible to identify subgroups of HNSCC patients who are highly curable with radiotherapy, or who are excellent candidates for clinical trials on hypoxia-targeting drugs in two distinct pathways.
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Koukourakis
authors.forename: Søren M
authors.initials: SM
authors.lastname: Bentzen
authors.forename: Alexandra
authors.initials: A
authors.lastname: Giatromanolaki
authors.forename: George D
authors.initials: GD
authors.lastname: Wilson
authors.forename: Frances M
authors.initials: FM
authors.lastname: Daley
authors.forename: Michele I
authors.initials: MI
authors.lastname: Saunders
authors.forename: Stanley
authors.initials: S
authors.lastname: Dische
authors.forename: Efthimios
authors.initials: E
authors.lastname: Sivridis
authors.forename: Adrian L
authors.initials: AL
authors.lastname: Harris
mesh_terms: D000951:Antigens, Neoplasm / Q000032:analysis / Q000096:biosynthesis*; D051792:Basic Helix-Loop-Helix Proteins / Q000032:analysis / Q000096:biosynthesis*; D014408:Biomarkers, Tumor / Q000032:analysis*; D001706:Biopsy; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000032:analysis / Q000096:biosynthesis*; D015687:Cell Hypoxia; D019583:Dose Fractionation, Radiation; D020869:Gene Expression Profiling; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D006801:Humans; D007150:Immunohistochemistry; D012189:Retrospective Studies; D016896:Treatment Outcome; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D000951:Antigens, Neoplasm; D051792:Basic Helix-Loop-Helix Proteins; D014408:Biomarkers, Tumor; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D000099162:Endothelial PAS Domain-Containing Protein 1; C089226:CA9 protein, human