RESUMEN
The changes in tissue temperature of basal cell carcinoma lesions were investigated during photodynamic therapy in order to better understand the effects and mechanisms of PDT in tissue. In this study, the monitoring of 40 lesions of basal cell carcinoma was performed during photodynamic therapy. The lesion region becomes thermally evident throughout the procedure, and there is an improved contrast of the lesion edges after the end of the irradiation. The comparison between thermal and fluorescence images showed a correlation between the PpIX evidenced through widefield fluorescence and the temperature gradient of the thermal images after the procedure, indicating that thermography is a potential diagnostic tool to evaluate the selective response of PDT. A model was created to calculate the amount of light energy converted to heat, tissue damage, and other energy transfer processes involved in the PDT. Using this model, it was shown that most of the energy conversion was in photodynamic action (48.7% and 48.3%, in first and second session, respectively), followed by the energy ratio attributable to blood perfusion (37.2%). This is evidence that photodynamic therapy does not generate a significant thermal component, an important aspect of the study of its mechanisms.
Asunto(s)
Carcinoma Basocelular/tratamiento farmacológico , Fotoquimioterapia/métodos , Fármacos Fotosensibilizantes/farmacocinética , Protoporfirinas/farmacocinética , Anciano , Carcinoma Basocelular/diagnóstico por imagen , Carcinoma Basocelular/patología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Imagen Óptica , TermografíaRESUMEN
BACKGROUND: Photodynamic Therapy (PDT) is a treatment for non-melanoma skin cancer. One of the main challenges of topical PDT is to increase the precursor penetration when applied on the lesion. Protoporphyrin IX (PpIX) is an endogenous photosensitizer (PS) widely used, obtained by the administration of precursors such as aminolevulinic acid and methyl aminolevulinate. Aiming for the technique improvement by providing greater PS penetration in skin lesions, we tested a new approach for drug delivery with a minimally invasive technique. A dermograph is a device currently used in aesthetic procedures to promote skin rejuvenation or to micropigmentation. The use of dermograph for drug delivery has not been particularly explored for PDT so far, and the present study explores that approach as its main goal. METHODS: This study evaluated the PpIX distribution and PDT damage in normal rat skin model; the response of dermograph application in a pilot clinical study was also investigated. RESULTS: The animal tests showed that more homogeneous PpIX distribution and greater penetration in the tissue was observed with dermograph when compared to the topical application. Six nodular basal cell carcinoma lesions were treated with PDT using intradermal delivery by dermograph, and no recurrence was observed after 28 months of follow-up. CONCLUSIONS: The precursor's penetration improvement and the consequent increase in PpIX distribution in-depth both favor PDT response, providing upgrades concerning problems that hinder the clinical practice acceptance.