title: Quantification of patient-reported outcome measures of radiation-induced skin reactions for use in clinical trial design.
abstract: Skin toxicity is a common effect from radiotherapy, although difficult to predict on an individual basis, and there is little evidence-based management. This study aimed to quantify inter-patient variation in patient-reported outcome measures for radiation-induced skin reactions (RISR) to enable the determination of the number of patients required for adequate power in a comparative trial of RISR management strategies.
  
  
  
  The study included 154 patients scheduled to receive breast cancer radiotherapy. Patients filled in a weekly questionnaire during and up to 4 weeks following the end of radiotherapy scoring five aspects of their experience of RISR: skin redness, and bother from redness like itching, burning sensation and tenderness/pain.
  
  
  
  Assessment of patients' reported experience of their RISR was shown to be feasible, with 91 % of patients returning at least two questionnaires. The mean score increase between weeks 1 and 4 was 25 points (p value <0.0001, 95 % CI 21-29), and the estimated standard deviation at 4 weeks was 18 (95 % CI 16-21).
  
  
  
  Patients' assessment of their reaction was not predicted on the basis of treatment and patient-related characteristics. Based on the observed variance in scores at 4 weeks, we could calculate the sample size required for a comparative study of two RISR management policies would be 200 patients to have statistical power to detect a clinically significant difference in patient-rated scores of their skin reactions. A trial employing this tool would help provide an evidence base to guide policy in advising patients how to manage their RISR.
authors.affiliation: Department of Radiotherapy, The Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands. n.russell@nki.nl.
authors.forename: N S
authors.initials: NS
authors.lastname: Russell
authors.affiliation: Department of Biometrics, The Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: van Werkhoven
authors.affiliation: Division of Psychosocial Research and Epidemiology, The Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
authors.forename: S B
authors.initials: SB
authors.lastname: Schagen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000150:complications* / Q000532:radiotherapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D012871:Skin Diseases / Q000139:chemically induced*; D011795:Surveys and Questionnaires
keywords: Patient-reported outcome measures (PROM); Radiation dermatitis; Radiation toxicity