Digital photography as source documentation of skin toxicity: An analysis from the Trans Tasman Radiation Oncology Group (TROG) 04.01 Post-Mastectomy Radiation Skin Care Trial

Introduction: This study evaluated digital photographs as a method of providing auditable source documentation for radiotherapy-induced skin toxicity and the possibility therefore of centralised, blinded scoring for a multicentre randomised controlled trial. Methods: Digital photograph sets from the first five patients from each of 12 participating centres were audited. Minimum camera specifications and photograph requirements were protocol specified. Three readers rated photographs for four key quality items. They also scored skin reactions according to National Cancer Institute Common Terminology Criteria (CTC) v3.0 acute skin score and also for the presence of any moist desquamation. Results: Five hundred fifty-two images were available. Field of view was scored as inadequate in 1–10%, focus inadequate in 0.4–4%, lighting inadequate in 0.2–3% and dividing line marking inadequate for scoring of skin reactions within sectors in 18–23% of photographs by three readers. Reader pairwise inter-observer agreement was 83–88% for CTC acute skin scores, but the kappa value ranged from 0.58 to 0.73. The percentage of image sectors not scored by readers due to difficulty in assessing was 1–10%. Moist desquamation was scored by clinicians in 8 (medial)–13% (lateral) of patients compared with 3–5% and 5–11% by readers. Conclusion: Photo reader inter-observer agreement is only moderate. Photo readers tended to underscore the frequency of moist desquamation, but the trend by sector parallels the clinical scorers. Photographs are useful source documents for auditing and monitoring, but not a replacement for clinical scoring.