title: Hyperbaric oxygenation for tumour sensitisation to radiotherapy.
abstract: BACKGROUND
  Cancer is a common disease and radiotherapy is one well-established treatment for some solid tumours. Hyperbaric oxygenation therapy (HBOT) may improve the ability of radiotherapy to kill hypoxic cancer cells, so the administration of radiotherapy while breathing hyperbaric oxygen may result in a reduction in mortality and recurrence.
  
  
  OBJECTIVE
  To assess the benefits and harms of radiotherapy while breathing HBO.
  
  
  METHODS
  In March 2011 we searched The Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, Issue 3), MEDLINE, EMBASE, DORCTHIM and reference lists of articles.
  
  
  METHODS
  Randomised and quasi-randomised studies comparing the outcome of malignant tumours following radiation therapy while breathing HBO versus air.
  
  
  METHODS
  Three review authors independently evaluated the quality of the relevant trials and extracted the data from the included trials.
  
  
  RESULTS
  Nineteen trials contributed to this review (2286 patients: 1103 allocated to HBOT and 1153 to control). With HBOT, there was a reduction in mortality for head and neck cancers at both one year and five years after therapy (risk ratio (RR) 0.83, P = 0.03, number needed to treat (NNT) = 11; and RR 0.82, P = 0.03, NNT = 5 respectively), as well as improved local tumour control at three months (RR with HBOT 0.58, P = 0.006, NNT = 7). The effect of HBOT varied with different fractionation schemes. Local tumour recurrence was less likely with HBOT at one year (head and neck: RR 0.66, P < 0.0001, NNT = 5), two years (uterine cervix: RR 0.60, P = 0.04, NNT = 5) and five years (head and neck: (RR 0.77, P = 0.01, NNT = 6). Any advantage is achieved at the cost of some adverse effects. There was a significant increase in the rate of both severe radiation tissue injury (RR 2.35, P < 0.0001, (number needed to harm (NNH) = 8) and the chance of seizures during therapy (RR 6.76, P = 0.03, NNH = 22) with HBOT.
  
  
  CONCLUSIONS
  There is some evidence that HBOT improves local tumour control and mortality for cancers of the head and neck, and local tumour recurrence in cancers of the head and neck, and uterine cervix. These benefits may only occur with unusual fractionation schemes. HBOT is associated with significant adverse effects including oxygen toxic seizures and severe tissue radiation injury. The methodological and reporting inadequacies of the studies included demand a cautious interpretation. More research is needed for head and neck cancer, but is probably not justified for bladder cancer. There is little evidence available concerning malignancies at other anatomical sites on which to base a recommendation.
authors.affiliation: Department of Anaesthesia, Prince of Wales Hospital, Randwick, Australia. m.bennett@unsw.edu.au
authors.forename: Michael H
authors.initials: MH
authors.lastname: Bennett
authors.forename: John
authors.initials: J
authors.lastname: Feldmeier
authors.forename: Robert
authors.initials: R
authors.lastname: Smee
authors.forename: Christopher
authors.initials: C
authors.lastname: Milross
mesh_terms: D001984:Bronchial Neoplasms / Q000401:mortality / Q000532:radiotherapy; D003131:Combined Modality Therapy / Q000379:methods; D004938:Esophageal Neoplasms / Q000401:mortality / Q000532:radiotherapy; D005260:Female; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000532:radiotherapy; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000009:adverse effects / Q000379:methods*; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology; D009369:Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D011836:Radiation Tolerance; D016032:Randomized Controlled Trials as Topic; D012004:Rectal Neoplasms / Q000401:mortality / Q000532:radiotherapy; D013997:Time Factors; D001749:Urinary Bladder Neoplasms / Q000401:mortality / Q000532:radiotherapy; D002583:Uterine Cervical Neoplasms / Q000401:mortality / Q000532:radiotherapy