A clinical investigation to determine the effect of pressure injection on the penetration of topical methyl aminolevulinate into nodular basal cell carcinoma of the skin

This investigation considered a novel method of enhancing penetration of the topical photosensitizing agent methyl aminolevulinate (MAL) into nodular basal cell carcinomas (BCCs) using an oxygen pressure injection device. Oxygen pressure injection (OPI) is a method to drive compounds into skin using pressured oxygen. The study was an observer-blinded pilot of a single application of MAL to nBCCs, with or without the use of OPI. The BCCs were then excised at different time intervals (0-180 min) and the depth of penetration of the MAL examined using microscopic fluorescence photometry to detect the production of the naturally fluorescent active photosensitiser protoporphyrin IX (PpIX). A highly selective and homogeneous distribution of MAL-induced porphyrin fluorescence was seen in all nBCC tumors studied, and showed a high lesion-to-normal-tissue ratio with very little fluorescence in the surrounding normal tissue. Although it was difficult to compare quantitatively, as individual tumors in each of the different study groups varied, a definite trend of increase in relative tumor concentration of MAL-induced PpIX was observed over time, and this was enhanced when OPI was employed.