British Journal of Dermatology | 2021
PD02: A prospective objective pilot study to assess the relationship between protoporphyrin IX fluorescence and skin surface temperature during photodynamic therapy
Abstract
PD01 A randomized single-blinded prospective study to compare short incubation white light-emitting diode photodynamic therapy (PDT) with conventional PDT for the treatment of squamous cell carcinoma in situ O. Tummon, E. NicDhonncha, R. Hellen, A. Havelin, J. Clowry, P. Collins and B. Moriarty Charles Institute of Dermatology, St. Vincent’s University Hospital, Dublin, IrelandConventional photodynamic therapy (cPDT) and daylight photodynamic therapy (dPDT) are effective treatments for squamous cell carcinoma in situ (SCCis). Their use is limited by pain and optimal weather conditions, respectively. Artificial white light PDT (WL PDT) has documented efficacy in treating actinic keratoses. We aimed to show noninferiority of WL PDT vs. standard cPDT in the treatment of SCCis. Noninferiority in this study was defined as a < 15% difference in clearance at 12 months. Secondary endpoints included tolerability of treatment. Patients were recruited from keratinocyte cancer clinics. A biopsy was taken to confirm the diagnosis and to rule out invasive disease. Patients were randomized to treatment with cPDT or WL PDT. To photosensitize the treatment area METVIX (160 mg g methyl aminolaevulinate) was applied 30 min before WL PDT and 3 h before cPDT. To achieve the prescribed dose of 75 J cm in the WL PDT cohort, an artificial light source – Maquet white light-emitting diode theatre light – was used. This emits light in the visible range only. In the cPDT cohort, the prescribed dose of 75 J cm was met using Omnilux (a red light source). All participants had two treatment sessions 7 days apart. The efficacy of treatment was assessed by clinicians blinded to the treatment arm at days 7 and 28, and 3, 6, 9 and 12 months posttreatment. Pain associated with treatment was measured using a visual analogue scale (VAS). Fifty-five patients were eligible for inclusion. Seven participants withdrew before starting treatment (n = 48). Twenty-five patients were randomized to cPDT and 23 to WL PDT. Median age was 76 years (range 55–93 years). Thirty-six were female. At 3 months post-treatment, reoccurrence rates were 26% (n = 6/23) in the WL PDT group and 12% (n = 3/25) in the cPDT group. One year post-treatment 22% (n = 5/23) of WL PDT patients and 72% (n = 18/25) of the cPDT group had maintained clearance. Peak average pain scores on the VAS during treatment were four times higher in the cPDT (40/100) group than the WL PDT group (10/100). In this study, we failed to show noninferiority of WL PDT when compared with cPDT for the treatment of SCCis. This is in contrast to the literature on actinic keratosis. Reporting well-designed negative studies is important to help plan future research and avoid exposing patient populations to treatments that have been previously proven to be ineffective.