Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study.

The research article discusses a pilot study conducted to examine the safety and efficacy of a new treatment for periocular squamous cell carcinoma, a type of cancer, in horses. The treatment combines surgical excision with photodynamic therapy (PDT), a method involving a special drug that becomes active when exposed to light.

Research Objectives and Methodology

The objective of this study was to validate the hypothesis that combining surgical resection with local photodynamic therapy (PDT) is a safe and effective treatment for equine Periocular Squamous Cell Carcinoma (PSCC). The method used was:

• performing surgical removal of as much of the tumor as possible,
• injecting the wound area with a drug known as HPPH,
• and then exposing the area to light of a specific wavelength emitted by a diode laser.

This procedure was carried out on nine horses (involving ten eyes), each suffering from PSCC.

Study Results

The results showed that after undergoing the treatment, the horses remained free of the disease for a period of 25-68 months. This outcome was achieved after a single treatment in seven horses and two treatments in one horse. However, one horse did develop ‘carcinoma in situ’ (CIS) or an early stage of cancer, 2.5 months after partial surgical resection and PDT treatment. This necessitated another round of local excision under sedation.

Conclusions and Future Directions

The findings suggest that through surgical excision coupled with PDT, it is possible to safely and effectively treat PSCC in horses. Nevertheless, to draw comprehensive conclusions, more research is required. Future studies should aim to assess and compare PDT treatment with current treatment procedures for PSCC in horses. It is also important to scrutinise variables like tumor recurrence rate, length of hospital stay, number of treatments required to eliminate the tumor, and the overall treatment costs in a controlled setting. The preliminary results from this pilot study indicate potential for adopting this novel treatment in addressing PSCC in horses.