Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study.
OBJECTIVE
Local photodynamic therapy (PDT) is a novel cancer therapy in veterinary ophthalmology. A prospective pilot study seeking to demonstrate proof of principle and safety for the treatment of equine periocular squamous cell carcinoma (PSCC) was therefore conducted. We hypothesized that surgical excision with adjunctive local PDT is an effective and safe treatment for equine PSCC.


METHODS
Nine horses (10 eyes) with PSCC were treated with surgical resection, local infiltration of resulting wound beds with 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH) and irradiation with 665-nm wavelength diode laser. Regular follow-up ophthalmic examinations were performed.


RESULTS
Surgical resection and PDT yielded disease-free intervals of 25-68 months in our study horses as of January, 2008. These results were obtained following a single treatment in seven horses and two treatments in one horse. In one horse, carcinoma in situ developed 2.5 months after partial surgical excision and PDT, requiring local excision under standing sedation.


CONCLUSIONS
Preliminary results suggest that surgical resection and adjunctive local PDT is a safe and effective novel treatment for PSCC in horses. More research is needed before PDT for the treatment of equine PSCC can be adequately compared with other current modalities. Important to future investigations regarding PDT, tumor recurrence rate, length of hospitalization, number of treatment episodes required to effect tumor remission, and total treatment costs should be examined in a controlled manner. Our present results and experiences suggest that this treatment may be useful in the treatment of equine PSCC.
Giuliano
Elizabeth A
EA
Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri-Columbia, Columbia, MO 65211, USA. giulianoe@missouri.edu
MacDonald
Ian
I
McCaw
Dudley L
DL
Dougherty
Thomas J
TJ
Klauss
Gia
G
Ota
Juri
J
Pearce
Jacqueline W
JW
Johnson
Philip J
PJ
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000401:mortality / Q000601:surgery / Q000662:veterinary*; D003131:Combined Modality Therapy / Q000662:veterinary; D018572:Disease-Free Survival; D005134:Eye Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000601:surgery / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy* / Q000401:mortality / Q000601:surgery; D006736:Horses; D008297:Male; D010778:Photochemotherapy / Q000379:methods / Q000662:veterinary*; D010865:Pilot Projects; D011446:Prospective Studies; D016896:Treatment Outcome