PHOTODYNAMIC THERAPY USING A DIODE-LASER WITH MONO-L-ASPARTYL CHLORINE6 FOR IMPLANTED FIBROSARCOMA IN MICE

We have developed a new high-power red (664 nm) laser diode system for photodynamic therapy (PDT) with mono-L-aspartyl chlorin e6 (NPe6). Me th-A fibrosarcoma cells (1X10(6)) were implanted subcutaneously in the right hind leg of 4-week-old BALB/c female mice. One week later, diod e laser irradiation was applied 5 h after the intravenous administrati on of NPe6 to each tumor-bearing mouse. In the first study, the time c ourse of intratumor temperature increase during PDT was measured by us ing a 23-guage thermocouple hypodermic needle at a depth of 2 mm from the tumor surface. In the second study, 6 groups of 10 to 17 tumor-bea ring mice were treated with the diode laser 5 h after intravenous admi nistration of NPe6 at the dose of 1.25, 2.5, 5.0 or 7.5 mg/kg i.v. per mouse. Total photoirradiation ranged from 0 to 150 J/cm(2) and the do se rate was adjusted to 100 mW/cm(2). Percentages of cures were determ ined from numbers of mice apparently disease-free 50 days after treatm ent. The results showed that this diode laser is effective in PDT of i mplanted fibrosarcoma after NPe6 administration. It also confirmed tha t the therapeutic effects of PDT were not due to hyperthermia. Moreove r, the diode laser beam was demonstrated by CCD technology to be unifo rm in intensity throughout the photoirradiated field.