title: Proton therapy - a systematic review of clinical effectiveness.
abstract: OBJECTIVE
  Proton therapy is an emerging treatment modality for cancer that may have distinct advantages over conventional radiotherapy. This relates to its ability to confine the high-dose treatment area to the tumour volume and thus minimizing radiation dose to surrounding normal tissue. Several proton facilities are currently operating or under planning world-wide - in the United States, Asia and Europe. Until now no systematic review assessing the clinical effectiveness of this treatment modality has been published.
  
  
  METHODS
  A systematic review of published studies that investigated clinical efficacy of proton therapy of cancer.
  
  
  RESULTS
  We included 54 publications: 4 randomized controlled trials (RCTs) reported in 5 publications, 5 comparative studies and 44 case series. Two RCTs addressed proton irradiation as a boost following conventional radiation therapy for prostate cancer, where one demonstrated improved biochemical local control for the highest dose group without increased serious complication rates. Proton therapy has been used to treat a large number of patients with ocular tumours, but except for one low quality RCT, no proper comparison with other treatment alternatives has been undertaken. Proton therapy offers the option to deliver higher radiation doses and/or better confinement of the treatment of intracranial tumours in children and adults, but reported studies are heterogeneous in design and do not allow for strict conclusions.
  
  
  CONCLUSIONS
  The evidence on clinical efficacy of proton therapy relies to a large extent on non-controlled studies, and thus is associated with low level of evidence according to standard heath technology assessment and evidence based medicine criteria.
authors.affiliation: Rikshospitalet-Radiumhospitalet Medical Center, University of Oslo, Oslo, Norway. d.r.olsen@medisin.uio.no
authors.forename: Dag Rune
authors.initials: DR
authors.lastname: Olsen
authors.forename: Oyvind S
authors.initials: OS
authors.lastname: Bruland
authors.forename: Gunilla
authors.initials: G
authors.lastname: Frykholm
authors.forename: Inger Natvig
authors.initials: IN
authors.lastname: Norderhaug
mesh_terms: D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D017063:Outcome Assessment, Health Care; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*; D013673:Technology Assessment, Biomedical; D011522:Protons
chemical_list: D011522:Protons