Photodynamic therapy for nasal and aural squamous cell carcinoma in cats.

Eighteen random-bred cats with a total of 19 nasal or aural squamous cell carcinomas were treated with photodynamic therapy, using aluminum phthalocyanine tetrasulfonate as the photosensitizer. Cats were irradiated at power densities of 100 mW/cm2 and energy densities of 100 J/cm2. Successful outcome was obtained in 10 tumors after 1 treatment, and 2 more tumors had complete responses after 1 or 2 additional treatments. Treatments were more effective in tumors of stage T2 or earlier. Five tumors had partial responses, and the response of 2 tumors could not be evaluated. The treatment was safe and well tolerated by most cats, although we found that cats should be kept out of sunlight for 2 weeks after treatment.