A research project funded by The HorseTrust has found that various types of equine ocular tumours can be successfully treated with mitomycin C, a cytotoxic antibiotic isolated from a bacterium.
Mitomycin C offers a safe and cost-effective alternative to current treatment options such as surgery and radiation.
Ocular tumours are more difficult to treat than tumours in other parts of the horse's body due to the risk of damaging the eye.
In the research project led by Fernando Malalana, while working as The Horse Trust's Clinical Scholar in Equine Internal Medicine at University of Liverpool, fourteen horses with eye-related squamous cell carcinoma, three of which were affected in both eyes, were treated during the study.
Mitomycin C was applied to the conjunctival sac of the affected eye; in some of the cases, the treatment was combined with surgery.
Malalana found that of the eight eyes treated with mitomycin C alone, clinical resolution occurred in six cases. Of the nine eyes treated with both surgery and mitomycin C, clinical resolution occurred in seven cases.
Mitomycin C was also used to treat various types of sarcoids found in the eye. Six horses and two donkeys with eye sarcoids, including one horse that was affected in both eyes, were treated with mitomycin C, which was injected directly into the tumour.
Malalana found that of the nine nodular and fibroplastic eye sarcoids treated with the antibiotic, all were completely cleared. However, the vets did not have good results with verrucous sarcoids.
"The results of this research should offer hope to the owners of horses that have eye tumours," Malalana said. "We have already been contacted by vets from across Europe to find out more information about this treatment and hope that it will be offered to more horses with occular tumours in the future."
Vets at the University of Liverpool are now testing the use of mitomycin C on other tumours that are difficult to treat surgically, including melanomas near the horse's anus. So far, two cases have been treated, but it is too early to tell whether treatment has been successful.
Malalana's research has been submitted to Veterinary Ophthalmology journal.