Intralesional interferon alpha-2b as a novel treatment for periocular squamous cell carcinoma in horses.
Authors: Martabano Brittany B, Dow Steven, Chow Lyndah, Williams Margaret M V, Mack Maura K, Bellone Rebecca, Wotman Kathryn L
Journal: PloS one
Summary
# Intralesional Interferon Alpha-2b for Equine Periocular Squamous Cell Carcinoma Periocular squamous cell carcinoma (PSCC) represents a significant clinical challenge in equine practice, and this prospective clinical trial evaluated whether direct perilesional injection of human recombinant interferon alpha-2b (IFNα2b) could offer a viable treatment option for systemically healthy horses with histologically confirmed disease. Eleven horses (12 eyes) received four to six fortnightly injections of 10 million IU IFNα2b whilst sedated, with tumour measurements recorded before each injection and at one, three, and 12 months post-treatment; response was defined as ≥50% size reduction. The intervention demonstrated both safety and modest efficacy: five of 12 eyes (representing 4/11 horses) achieved positive response, including two eyes with complete gross resolution of tumour tissue, whilst local swelling occurred in six horses but resolved spontaneously; notably, all horses developed serum anti-IFNα2b antibodies, yet no statistical difference in antibody concentration distinguished responders from non-responders, suggesting treatment failure was unrelated to immune neutralisation. For practitioners managing PSCC in horses, this represents a well-tolerated alternative when surgical excision or other modalities are contraindicated, though the 42% response rate warrants careful case selection and realistic prognostic discussion with owners; the mechanism underpinning treatment success versus failure remains incompletely understood and merits further investigation to optimise patient stratification.
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Practical Takeaways
- •Intralesional interferon alpha-2b offers a novel, non-invasive treatment option for periocular squamous cell carcinoma with a 42% response rate and minimal systemic side effects—local swelling is expected but self-resolving
- •Treatment failure does not appear related to antibody development, suggesting other factors may determine response; this technique could be offered as an alternative to surgery or radiotherapy in suitable cases
- •Standard protocol consists of 4-6 injections spaced every two weeks with sedation; tumors should be measured at baseline and at 1, 3, and 12 months post-treatment to assess response
Key Findings
- •Perilesional interferon alpha-2b induced tumor regression in 5 of 12 eyes (42% response rate), with 2 eyes showing complete resolution
- •Treatment was well-tolerated with only local swelling in 6/11 horses during protocol, resolving without intervention and no systemic adverse effects
- •All 11 horses developed serum anti-IFN-α2b antibodies, but antibody concentration showed no statistical difference between responders and non-responders
- •Horses received 4-6 perilesional injections of 10 million IU IFN-α2b administered every two weeks