| First Author | Van der Veen N | Year | 1997 |
| Journal | Int J Cancer | Volume | 72 |
| Issue | 1 | Pages | 110-8 |
| PubMed ID | 9212231 | Mgi Jnum | J:41379 |
| Mgi Id | MGI:893823 | Doi | 10.1002/(sici)1097-0215(19970703)72:1<110::aid-ijc16>3.0.co;2-n |
| Citation | Van der Veen N, et al. (1997) Photobleaching during and re-appearance after photodynamic therapy of topical ALA-induced fluorescence in UVB-treated mouse skin. Int J Cancer 72(1):110-8 |
| abstractText | Photodynamic therapy (PDT) using protoporphyrin IX (PpIX) induced by topically applied 5-aminolevulinic acid (ALA) seems a promising alternative for the treatment of superficial non-melanoma skin cancer and actinic keratosis. In this study, the kinetics of new PpIX fluorescence arising after a PDT treatment that had photobleached the original fluorescence were determined. Our purpose was to examine the feasibility of multiple irradiations, following a single topical ALA application, to increase PDT efficacy. In addition, photobleaching during PDT and the fluorescence spectra during and after PDT were studied. As a model we used hairless mice with and without UVB-induced skin lesions. ALA was applied to the skin for 4 hr. An illumination was delivered either immediately after application or 6 hr after the end of the application (at interval of maximum fluorescence). During PDT, the fluorescence of normal skin decreased at a faster rate than the fluorescence of the skin lesions. In the fluorescence study after PDT, the areas treated immediately post-application showed a fluorescence increase over time similar to that in non-treated areas on the same mice. A remarkable result was that the fluorescence of areas treated at maximum fluorescence increased, whereas the fluorescence of non-treated areas did not increase over time. With both treatment intervals the new fluorescence showed a characteristic PpIX spectrum. Our results demonstrate that a second illumination, when new PpIX fluorescence has been formed, may increase PDT efficacy after topical ALA application. This finding has been demonstrated previously for systemic ALA administration. |
