Photodynamic therapy of facial squamous cell carcinoma in cats using a new photosensitizer

✍ Scribed by Magne, Michael L.; Rodriguez, Carlos O.; Autry, Susan A.; Edwards, Benjamin F.; Theon, Alain P.; Madewell, Bruce R.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 454 KB
• Volume: 20
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/(sici)1096-9101(1997)20:2<202::aid-lsm12>3.0.co;2-h

✦ Synopsis

Background and Objective: Photodynamic therapy has been shown to be an effective treatment modality for surface-oriented neoplasms of the skin, respiratory, gastrointestinal, and urogenital systems. The purpose of this study was to assess the safety and efficacy of photodynamic therapy using a new photosensitizer in the treatment of squamous cell carcinomas of the feline facial skin. Study Design/Materials and Methods: Cats with naturally occurring squamous cell carcinomas of the facial skin were entered into the study. Tumors were staged using a modification of the World Health Organization (WHO) system for classification of feline tumors of epidermal origin. Photodynamic therapy was delivered to the tumors using an argon-pumped dye laser 24 hours after the administration of the photosensitizer pyropheophorbide-alpha-hexyl-ether (HPPH-23). Following treatment, tumors were evaluated for complete response rates and local control durations. Results: Fifteen tumors were staged T1a (< 1.5 cm diameter, noninvasive), 18 T1b (< 1.5 cm, invasive), and 28 T2B (> 1.5 cm, invasive). Complete response rates as well as local control durations were significantly (P < 0.05) related to stage. Complete response was achieved in 100% of T1a tumors, 56% of T1b tumors, and 18% of T2b tumors. One-year local control rates were 100% for T1a tumors and 53% for T1b tumors; overall 1-year local control rate for all treated tumors was 62%. Clinical, hematological, and biochemical evidence of toxicity was not seen in any cat following drug administration. However, morbidity was observed following treatment of large, invasive tumors of the nasal plane. Conclusion: Photodynamic therapy with the photosensitizer HPPH-23 was safe and effective in treating early stage squamous cell carcinomas of the feline nasal plane and facial skin. How-