Katsuo Aizawa

Photoradiation Therapy with Hematoporphyrin Derivative and an Argon Dye Laser of Bladder Carcinoma

Hematoporphyrin Derivative (HpD) which has an affinity for malignant tumors is excited by light exposure and reacts photodynamically in tumor tissue. Therefore it is possible to treat malignant tumor selectively without any damage to surrounding normal tissues. HpD is excited by a light in the spectrum from ultraviolet to visible red. Previously arc lamps and slide projectors were used for excitation of HpD but laser beams which facilitate photoradiation via endoscopes has been used recently. Much of the early basic and clinical studies on HpD and light photoradiation therapy was performed by Dougherty and his coworkers1. Hayata et al. investigated photoradiation therapy using an argon dye laser following an intravenous HpD administration in mice, and on cultured human lung cancer cells2, and in experimentally induced canine lung cancer and demonstrated its therapeutic effectiveness3. Malignant bladder tumor were treated by this new technique in this study.

Fluorescence photodiagnosis for malignant tumor

The effectiveness of a new excimer laser endoscopic imaging fluorescence analyzer system using the photosensitizer, mono-L-aspartyl chlorin e6 (NPe6) for the detection of tumors was evaluated. Autofluorescence (550 plus or minus 10 nm, green fluorescence) from normal sites, red fluorescence (664 nm) of NPe6 in areas of cancer and the red fluorescence/green fluorescence ratio (R/G ratio) as the color image can be detected respectively. The greatest NPe6 fluorescence from the lesion was obtained at 3 hours after injection and the fluorescence disappeared at 24 hours. The greatest difference in the fluorescence of NPe6 and the R/G ratio in areas of tumor and in normal areas were observed at 5 hours after administration. At this period, NPe6 fluorescence from normal sites was negligible. These data suggest that fluorescence photodiagnosis may be effective in the detection of cancers.

Photodynamic therapy using a diode laser with mono-L-aspartyl chlorin e6 (NPe6)

The authors developed a new high-power red laser diode system (Matsushita Industrial Equipment Co., Ltd., Osaka) for photodynamic therapy (PDT) with mono-L-aspartyl chlorin e6 (NPe6, Meiji Seika Kaisha LTD.). The laser wavelength was adjusted to 664 nm and the power output could be varied in the range of 50-500 mW at the fiber tip in a continuous wave (cw) mode. The delivered energy could be adjusted from 50 - 1000 J. The system has a size of 49 by 20 by 40 cm, weighs 20 kg, and is readily portable. It runs on 100 V current. The laser power is easily controlled and the wavelength is stable (less than plus or minus 0.2 nm). The output beam is delivered via a quartz fiber. Furthermore, the full width at half-maximum power is less than 2 nm, which enables uniform, high-density photoirradiation. The power density distribution of the laser, analyzed by a CCD camera, was uniform throughout the photoirradiated field. In an animal study, tumor-bearing Balb/c mice were treated with the diode laser 5 hours after intravenous administration of NPe6 at a dose of 1.25 to 12.5 mg/kg i.v.. Total photoirradiation ranged from 3.13 to 250 J/cm2 which the energy density was adjusted to 100 mW/cm2. Percentages of cures were determined histopathologically from numbers of mice apparently disease-free 1 week after treatment. The results show that a laser energy of more than 12.5 J/cm2 was necessary to obtain 90% tumor cure rate at a maximum dose of NPe6 (12.5 mg/kg) and NPe6 dose of more than 2.5 mg/kg was necessary to obtain 90% cure rate at high laser energy of 200 J/cm2.

Effectiveness of photodynamic therapy with a diode laser using mono-L-aspartyl chlorin e6 for implanted fibrosarcoma in mice

The authors developed a new high power red laser diode system for photodynamic therapy (PDT) with Mono-L-aspartyl Chlorin e6 (NPe6). The laser beam has a low wavelength (664 nm) and relatively high power. Our results suggest that a certain increase in the tumor tissue level of NPe6 and a certain increase of laser light dose reaching a deeper layer of tumor caused an increase in percent cure. In addition, the effectiveness of PDT and also tumor recurrence following PDT depend to some extent on the total laser dose reaching deeper layers of tumors. Furthermore, the effectiveness of PDT tends to correlate with the amount of photobleaching by PDT.