In-vivo fluorescence dosimetry of aminolevulinate-based protoporphyrin IX (PpIX) accumulation in human nonmelanoma skin cancers and precancers

Christine B. Warren; Sara Lohser; Sung Chang; Philip A. Bailin; Edward V. Maytin

doi:10.1117/12.822966

13 July 2009 In-vivo fluorescence dosimetry of aminolevulinate-based protoporphyrin IX (PpIX) accumulation in human nonmelanoma skin cancers and precancers

Christine B. Warren, Sara Lohser, Sung Chang, Philip A. Bailin, Edward V. Maytin

Author Affiliations +

Proceedings Volume 7380, Photodynamic Therapy: Back to the Future; 73801M (2009) https://doi.org/10.1117/12.822966
Event: 12th World Congress of the International Photodynamic Association, 2009, Seattle, Washington, United States

Abstract

PDT is clinically useful for precancers (actinic keratoses; AK) of the skin, but the optimal duration for 5-ALA application is still controversial. For basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), cure rates remain inferior to surgical excision. Lack of knowledge about regional levels of PpIX levels within target tissues clearly contribute to these suboptimal results. To investigate PpIX levels achievable in human skin neoplasias in-vivo, a clinical study to monitor PpIX accumulation in vivo was performed. PpIX-fluorescence in patients undergoing ALA-PDT for facial AK was monitored via real-time in-vivo fluorescence dosimetry, with measurements q20 min following application of 5-ALA (Levulan Kerastick). PpIX accumulation followed linear kinetics in nearly all cases. The slopes varied widely, and did not correlate with clinical outcome in all patients. Some patients with a low accumulation of PpIX fluorescence had a good response to therapy, whereas others with high PpIX accumulation required repeat treatment (although not necessarily of the same lesion). PpIX accumulation rates did correlate to a certain degree with the overall amount of erythema. We conclude that unknown factors besides PpIX levels must be critical for the response to treatment. To assess the relationship between PpIX levels in various skin cancers, patients undergoing routine Mohs surgery for BCC or SCC were measured by in-vivo dosimetry at 2 h after 5-ALA application. Overall, a progressive increase in PpIX signal during malignant progression was observed, in the following rank order: Normal skin < AK < SCC ~ BCC.

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Christine B. Warren, Sara Lohser, Sung Chang, Philip A. Bailin, and Edward V. Maytin "In-vivo fluorescence dosimetry of aminolevulinate-based protoporphyrin IX (PpIX) accumulation in human nonmelanoma skin cancers and precancers", Proc. SPIE 7380, Photodynamic Therapy: Back to the Future, 73801M (13 July 2009); https://doi.org/10.1117/12.822966

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