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

Abstract

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. However, toxicity was encountered following treatment of large neoplasms.

• Authors: M L Magne, C O Rodriguez, S A Autry, B F Edwards, A P Theon, B R Madewell
• Journal: Lasers in surgery and medicine (Lasers Surg Med) Vol. 20 Issue 2 Pg. 202-9 ( 1997) ISSN: 0196-8092 [Print] United States
• PMID: 9047175 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Photosensitizing Agents
• Chlorophyll
• 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a

Topics

• Animals
• Carcinoma, Squamous Cell (drug therapy, pathology)
• Cats
• Chlorophyll (adverse effects, analogs & derivatives, therapeutic use)
• Edema (etiology)
• Inflammation
• Opportunistic Infections
• Photochemotherapy (adverse effects)
• Photosensitizing Agents (adverse effects, therapeutic use)
• Skin Neoplasms (drug therapy, pathology)