Photodynamic Therapy (PDT) using intratumoral injection of the 5- aminolevulinic acid (5-ALA) for the treatment of eye cancer in cattle Raduan Hage 1, 2 , Geraldo Mancilha 2 , Renato Amaro Zângaro 2 , Egberto Munin 2 , Hélio Plapler 1 1 – Universidade Federal de São Paulo – UNIFESP – Operative Technique and Experimental Surgery Division - Department of Surgery – São Paulo – Brazil. 2 – Universidade do Vale do Paraíba (UNIVAP) – Research and Development Institute - São José dos Campos (SP) – Brazil. raduan.dcir@epm.br ABSTRACT A six-year old Holstein cow with an eye cancer (ocular squamous cell carcinoma) involving the third eyelid and conjunctiva was submitted to photodynamic therapy using intratumoral 20% aminolevulinic acid (5-ALA - Aldrich Chemical Company, Milwaukee, USA) and a light emitting diode (LED - VET LED - MMOptics®) with wavelength between 600 and 700 nm, 2 cm diameter circular light beam, power of 150 mW, light dose of 50 J/cm 2 as a source of irradiation. Fifteen days after the experimental procedure we observed about 50% tumor reduction and complete remission after 3 months. Relapse was not observed up to 12 months after the treatment. Although the study only includes one animal not allowing definite conclusions, it indicates that PDT represents a safe and technically feasible approach in the treatment of eye cancer in cattle. Keywords: Photodynamic therapy; 5-ALA; Eye cancer; Cattle diseases INTRODUCTION Eye cancer (ocular squamous cell carcinoma) is the most common form of cancer in cattle. It is a skin cancer occurring on the eye and eyelids. Reports on the frequency and the distribution of the disease indicate that it is still a very prevalent and economically important disease 1 . Some of the predisposing factors are heritable, and in certain lines or families nearly all cattle may be affected during their lifetime 2, 3 . Etiological factors including ultraviolet light, circumocular apigmentation and viruses, as well as the pathogenesis, are considered in light of current knowledge on carcinogenesis of this tumor 1 . In spite of the relevant advancement in the traditional techniques (surgery, chemotherapy and radiotherapy) used in the treatment of the different types of neoplasias, those still present limited efficiency, as well as serious side effects. The Photodynamic Therapy (PDT) has been widely investigated in recent decades and is emerging as a promising therapy for a wide variety of malignant tumors in dogs, cats having naturally occurring 4, 5, 6, 7, 8 and human diseases like squamous cell carcinoma, basal cell carcinoma, melanoma 9 , non-oncological applications as aged related macular degeneration 10 . PDT is based on photoactivation by a given wavelength of a photosensitizer relatively retained by cancer cells, which produces highly reactive oxygen species that can destroy tumor cells with minimum side effects 11 . Several photosensitizer have been used in PDT, hematoporphyrin derivatives (HpD), sulfonated aluminum phthalocyanine, benzoporphyrin derivative, 5-aminolevulinic acid (5-ALA) among others 12 . Aminolevulinic acid is a prodrug that is metabolized intracellularly to form the photosensitizing molecule protoporphyrin IX (PpIX). When PpIX is activated by light, cytotoxic reactive oxygen species and free radicals are generated 13 . The intravenous and topical application of 5-ALA has been used in the treatment of superficial squamous cell carcinomas (SCC), basal cell carcinomas (BCC), Bowen’s disease, actinic keratoses 14, 15 . This study aimed to evaluate the Photodynamic Therapy (PDT) effects in eye cancer in a Holstein cow using intratumoral injection of 5-ALA and as source of irradiation a light emitting diode (LED - VET LED - MMOptics®). Please verify that (1) all pages are present, (2) all figures are acceptable, (3) all fonts and special characters are correct, and (4) all text and figures fit within the margin lines shown on this review document. Return to your MySPIE ToDo list and approve or disapprove this submission. 6427-48 V. 4 (p.1 of 7) / Color: No / Format: A4 / Date: 12/22/2006 5:02:02 AM SPIE USE: ____ DB Check, ____ Prod Check, Notes: