Tissue distribution and penetration of 5-ALA induced fluorescence in an amelanotic melanoma after topical application
Pahernik, S.; Langer, S.; Botzlar, A.; Dellian, M.; Goetz, A.E.
Anticancer Research 21(1a): 59-63
2001
ISSN/ISBN: 0250-7005 PMID: 11299790 Document Number: 526248
Background: Photodynamic therapy (PDT) following topical application of 5-aminolevulinic acid (ALA) is increasingly employed for several types of malignancies. However, data with respect to tissue penetration and distribution of ALA-induced porphyrins after topical application are scarce. Therefore, it was our aim to study tissue distribution and the penetration potency of topically applied ALA. Material and Methods: We used Syrian golden hamsters implanted with the amelanotic melanoma A-Mel-3 growing in a transparent dorsal skinfold chamber. ALA was topically applied in aqueous solution at a concentration of 3% for 4 hours. The fluorescence pattern was quantified by fluorescence microscopy and digital image analysis from cryosections and given as percentage of a reference standard in medians (25%, 75% quartiles). Results: Fluorescence intensities in tumors were 90.8% (56.2%, 115.2% of a reference standard, p<0.01 vs. normal tissue) significantly exceeding normal surrounding host tissue yielding fluorescence intensities of 12.1% (9.1%, 16.1%,). The tumor selectivity, that is the ratio of fluorescence intensities between tumor and normal tissue, was 7.3 (6.1, 9.1). For superficial tumors with a thickness of approximately 1 mm no fluroescence gradients after topical application of ALA could be observed. Conclusion: In superficial cancerous lesions the fluorescence distribution of ALA induced porphyrins is tumor selective without significant fluorescence gradients throughout the tumor. Thus, by optimising the treatment modalities for topical ALA-PDT an enhanced efficacy and selectivity will be reached.