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Photodynamic therapy of experimental subchoroidal melanoma using chloroaluminum sulfonated phthalocyanine
S A Ozler1, J S Nelson, P E Liggett
1Doheny Eye Institute, University of Southern California, Los Angeles.
Abstract:
Although photodynamic therapy has shown great promise for the treatment of a variety of malignant neoplasms, the role of this new therapeutic modality in the clinical management of intraocular tumors remains incompletely understood. This study examines the effects of photodynamic therapy using chloroaluminum sulfonated phthalocyanine on Greene hamster melanoma transplanted into the subchoroidal space in rabbits. Twenty-four hours after intravenous administration of chloroaluminum sulfonated phthalocyanine (5 mg/kg), tumors were irradiated with 675 nm of light at total light doses of 7 to 60 J/cm2. The results show that tumor growth was arrested at total light doses of 22 to 60 J/cm2. At total light doses of 15 to 21 J/cm2, tumor growth was initially arrested. However, regrowth of these tumors was apparent within 7 days. Total light doses of less than 15 J/cm2 showed no response. Complications of photodynamic therapy, such as intraretinal or subretinal hemorrhages and retinal detachment, were seen only in animals who received total light doses in excess of 43 J/cm2.
Insights
Photodynamic therapy using chloroaluminum sulfonated phthalocyanine effectively arrested Greene hamster melanoma growth in rabbits at light doses of 22 J/cm2 or higher. Doses above 43 J/cm2 were associated with complications.
Area of Science:
- Ophthalmology
- Oncology
- Photomedicine
Background:
- Photodynamic therapy (PDT) shows promise for various cancers.
- Its efficacy in treating intraocular tumors requires further investigation.
Purpose of the Study:
- To evaluate the effects of PDT using chloroaluminum sulfonated phthalocyanine on subchoroidal hamster melanoma in rabbits.
- To determine effective light doses and identify potential complications.
Main Methods:
- Greene hamster melanoma was transplanted into the subchoroidal space of rabbits.
- Chloroaluminum sulfonated phthalocyanine was administered intravenously (5 mg/kg).
- Tumors were irradiated with 675 nm light at doses ranging from 7 to 60 J/cm2.
Main Results:
- Tumor growth arrest was observed at light doses of 22 to 60 J/cm2.
- Initial tumor growth arrest occurred at 15 to 21 J/cm2, followed by regrowth within 7 days.
- No response was noted at light doses below 15 J/cm2.
- Complications including hemorrhages and retinal detachment occurred only at doses exceeding 43 J/cm2.
Conclusions:
- PDT with chloroaluminum sulfonated phthalocyanine can inhibit intraocular tumor growth in a dose-dependent manner.
- Optimal therapeutic light doses for PDT in this model range from 22 to 60 J/cm2.
- Higher light doses (above 43 J/cm2) increase the risk of ocular complications.