title: A double-blind placebo-controlled randomized clinical trial with magnesium oxide to reduce intrafraction prostate motion for prostate cancer radiotherapy.
abstract: OBJECTIVE
  To investigate whether magnesium oxide during external-beam radiotherapy for prostate cancer reduces intrafraction prostate motion in a double-blind, placebo-controlled randomized trial.
  
  
  METHODS
  At the Department of Radiotherapy, prostate cancer patients scheduled for intensity-modulated radiotherapy (77 Gy in 35 fractions) using fiducial marker-based position verification were randomly assigned to receive magnesium oxide (500 mg twice a day) or placebo during radiotherapy. The primary outcome was the proportion of patients with clinically relevant intrafraction prostate motion, defined as the proportion of patients who demonstrated in ≥ 50% of the fractions an intrafraction motion outside a range of 2 mm. Secondary outcome measures included quality of life and acute toxicity.
  
  
  RESULTS
  In total, 46 patients per treatment arm were enrolled. The primary endpoint did not show a statistically significant difference between the treatment arms with a percentage of patients with clinically relevant intrafraction motion of 83% in the magnesium oxide arm as compared with 80% in the placebo arm (p = 1.00). Concerning the secondary endpoints, exploratory analyses demonstrated a trend towards worsened quality of life and slightly more toxicity in the magnesium oxide arm than in the placebo arm; however, these differences were not statistically significant.
  
  
  CONCLUSIONS
  Magnesium oxide is not effective in reducing the intrafraction prostate motion during external-beam radiotherapy, and therefore there is no indication to use it in clinical practice for this purpose.
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands. i.m.lips@umcutrecht.nl
authors.forename: Irene M
authors.initials: IM
authors.lastname: Lips
authors.forename: Carla H
authors.initials: CH
authors.lastname: van Gils
authors.forename: Alexis N T J
authors.initials: AN
authors.lastname: Kotte
authors.forename: Monique E
authors.initials: ME
authors.lastname: van Leerdam
authors.forename: Stefan P G
authors.initials: SP
authors.lastname: Franken
authors.forename: Uulke A
authors.initials: UA
authors.lastname: van der Heide
authors.forename: Marco
authors.initials: M
authors.lastname: van Vulpen
mesh_terms: D000368:Aged; D002400:Cathartics / Q000008:administration & dosage*; D004311:Double-Blind Method; D057918:Fiducial Markers; D006801:Humans; D008277:Magnesium Oxide / Q000008:administration & dosage*; D008297:Male; D009068:Movement / Q000187:drug effects*; D011467:Prostate; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011788:Quality of Life; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
chemical_list: D002400:Cathartics; D008277:Magnesium Oxide