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Photodynamic therapy with endogenous protoporphyrin IX: basic principles and present clinical experience
J C Kennedy1, R H Pottier, D C Pross
1Department of Oncology, Queen's University, Kingston, Ontario, Canada.
Summary
Topical 5-aminolaevulinic acid (ALA) induces photosensitizing protoporphyrin IX (Pp IX) in abnormal skin cells. Subsequent light exposure selectively destroys lesions like basal cell carcinomas, showing high response rates and excellent cosmetic outcomes.
Area of Science:
- Biochemistry
- Dermatology
- Photodynamic Therapy
Background:
- 5-Aminolaevulinic acid (ALA) is a heme biosynthesis precursor.
- Exogenous ALA leads to protoporphyrin IX (Pp IX) accumulation in specific cells.
- Pp IX acts as a photosensitizer, causing cell damage upon light exposure.
Purpose of the Study:
- To evaluate the efficacy of ALA-induced photodynamic therapy (PDT) for skin lesions.
- To determine the selectivity of ALA-PDT in targeting abnormal epithelium.
- To assess treatment outcomes, including response rates and cosmetic results.
Main Methods:
- Topical application of ALA in aqueous solution to actinic keratoses and carcinomas.
- Exposure to photoactivating light to induce selective lesion destruction.
- Clinical trial monitoring treatment response and patient outcomes.
Main Results:
- ALA-PDT demonstrated selective Pp IX accumulation in abnormal epidermis.
- High response rates for basal cell carcinomas: 90% complete and 7.5% partial response after one treatment.
- Excellent cosmetic results and high patient acceptance were observed.
Conclusions:
- ALA-induced PDT is an effective and selective treatment for certain skin cancers and pre-cancerous lesions.
- The method offers a promising therapeutic option with favorable cosmetic outcomes.
- Targeted photosensitization via ALA provides a non-invasive approach to lesion removal.