PD02: A prospective objective pilot study to assess the relationship between protoporphyrin IX fluorescence and skin surface temperature during photodynamic therapy

TY - JOUR

T1 - PD02: A prospective objective pilot study to assess the relationship between protoporphyrin IX fluorescence and skin surface temperature during photodynamic therapy

AU - O'Mahoney, P.

AU - Samuel, I.

AU - Eadie, E.

AU - Ibbotson, S.

N1 - © 2021 British Association of Dermatologists

PY - 2021/7/1

Y1 - 2021/7/1

N2 - The reduced efficacy of topical photodynamic therapy (PDT) on the extremities, such as the hands and lower legs, highlights the need for improved understanding of underlying mechanisms in order to improve PDT outcomes. Both protoporphyrin IX (PpIX) fluorescence and skin surface temperature have been implicated as possible factors in the discrepancies between efficacies at different body sites; however, this has not been investigated in a clinical study. We carried out a pilot study, measuring PpIX fluorescence and skin surface temperature in order to gain a better understanding of how these two parameters interact and relate to treatment endpoints. Eighteen participants were recruited from a population referred for PDT with either Bowen disease or basal cell carcinoma. Exclusion criteria included previous treatment of skin lesion in the preceding 4 months or photosensitivity disease. Fluorescence was measured using a bespoke camera, which allowed for field‐of‐view (FOV) measurements, while temperature was measured using a thermal camera to achieve a similar FOV image. Fluorescence and skin surface temperature were measured at regular intervals during the prodrug incubation phase (every 30 min) and at set intervals (1, 2, 4, 8·5 and 17 min) during the PDT irradiation phase. Fluorescence intensity around a region of interest was determined for each time point and presented as fluorescence over time, and temperature similarly processed. Pain immediately after treatment was recorded on a visual analogue scale (0–10), and outcome at 3 and 12 months recorded. Both PpIX fluorescence and temperature were correlated with body site (lower leg and trunk), confirming a relationship hypothesized in a previous study, being significantly lower on the lower leg than the trunk. Although not powered to find a difference, neither parameter was correlated with efficacy, which was comparable across body sites (80% clear at 12 months). Patients reported significantly higher pain on the lower leg than on the trunk. The study supports the hypothesis that fluorescence and temperature are correlated with body site. The lack of firm data between fluorescence or temperature and efficacy supports future investigative studies, and the likelihood that PDT efficacy is dependent on multiple variables, which requires further study but potentially provides opportunities for optimization of treatment outcomes through a multitargeted approach.

AB - The reduced efficacy of topical photodynamic therapy (PDT) on the extremities, such as the hands and lower legs, highlights the need for improved understanding of underlying mechanisms in order to improve PDT outcomes. Both protoporphyrin IX (PpIX) fluorescence and skin surface temperature have been implicated as possible factors in the discrepancies between efficacies at different body sites; however, this has not been investigated in a clinical study. We carried out a pilot study, measuring PpIX fluorescence and skin surface temperature in order to gain a better understanding of how these two parameters interact and relate to treatment endpoints. Eighteen participants were recruited from a population referred for PDT with either Bowen disease or basal cell carcinoma. Exclusion criteria included previous treatment of skin lesion in the preceding 4 months or photosensitivity disease. Fluorescence was measured using a bespoke camera, which allowed for field‐of‐view (FOV) measurements, while temperature was measured using a thermal camera to achieve a similar FOV image. Fluorescence and skin surface temperature were measured at regular intervals during the prodrug incubation phase (every 30 min) and at set intervals (1, 2, 4, 8·5 and 17 min) during the PDT irradiation phase. Fluorescence intensity around a region of interest was determined for each time point and presented as fluorescence over time, and temperature similarly processed. Pain immediately after treatment was recorded on a visual analogue scale (0–10), and outcome at 3 and 12 months recorded. Both PpIX fluorescence and temperature were correlated with body site (lower leg and trunk), confirming a relationship hypothesized in a previous study, being significantly lower on the lower leg than the trunk. Although not powered to find a difference, neither parameter was correlated with efficacy, which was comparable across body sites (80% clear at 12 months). Patients reported significantly higher pain on the lower leg than on the trunk. The study supports the hypothesis that fluorescence and temperature are correlated with body site. The lack of firm data between fluorescence or temperature and efficacy supports future investigative studies, and the likelihood that PDT efficacy is dependent on multiple variables, which requires further study but potentially provides opportunities for optimization of treatment outcomes through a multitargeted approach.

U2 - 10.1111/bjd.20189

DO - 10.1111/bjd.20189

M3 - Meeting abstract

SN - 0007-0963

VL - 185

SP - 85

EP - 86

JO - British Journal of Dermatology

JF - British Journal of Dermatology

IS - S1

M1 - PD02

ER -