DETERMINATION OF THE MAXIMAL TUMOR NORMAL SKIN RATIO AFTER HPD OR M-THPC ADMINISTRATION IN HAIRLESS MOUSE (SKH-1) BY FLUORESCENCE SPECTROSCOPY - A NONINVASIVE METHOD/

Two major steps in our study on the treatment of skin tumors by photoc hemotherapy (PCT) were the development of a skin tumor model in heirle ss mice by chemical carcinogenesis and by the use fluorescence spectro scopy, a semi-quantitative and non-invasive method, to determine the t ime after i.p. injection of photosensitizer when the tumor/normal skin ratio is the highest. Carcinogenesis provided mice bearing many benig n papillomas and these were used to determine the tumor/normal skin ra tios of two photosensitizers by fluorescence spectroscopy. Hematoporph yrin derivative (HpD) (5 mg/kg body weight) and m-tetra(hydroxyphenyl) -chlorin (m-THPC) (0.3 mg/kg body weight) were injected, and fluoresce nce measured at 4, 8, 24, 48, 72 and 96 h after injection. The best tu mor/normal skin ratio was 6.2 for HpD and 5.1 for m-THPC. The times re quired to reach these ratios were 48 h for HpD and 72 h for m-THPC. Pu blished reports indicate that m-THPC gives a much higher tumor/normal skin ratio than HpD. These results must be confirmed by organic extrac tion. Photodynamic therapy with the same doses of HpD and m-THPC used in this pharmacokinetic study must also be carried out to compare the toxicities of the two photosensitizers and to determine which is best for this type of tumor.