Small Animal Review

Allergic or hypersensitivity dermatitis is not uncommonly described in dogs, and may be managed using a range of medical therapies including glucocorticoids, ciclosporin, oclacitinib (Apoquel; Zoetis), loviketmab (Cytopoint; Zoetis) and immunotherapy. In humans, long-term treatment with ruxolitinib, a related compound, has been associated with an increased risk of developing epidermal tumours (basal cell tumours and squamous cell carcinomas). In contrast, the use of tofacitinib, another inhibitor of janus-kinases (JAKs), has not been associated with significant adverse effects. The impact of using oclacitinib in dogs who have neoplasia is unclear, so a study assessing the risk of neoplasia in dogs treated over a long period with oclacitinib (Lancellotti et al, 2020) is welcome.

The study, published in JAVMA, was a retrospective analysis of data from dogs receiving treatment for allergic dermatitis with or without oclacitinib. The study population of dogs with allergic dermatitis comprised 339 dogs that had received oclacitinib for more than 6 months and 321 dogs that had never been prescribed the drug. In the group exposed to oclacitinib treatment, times ranged from 6–58 months and the sum total follow-up duration was 1105.6 patient years. The unexposed group had been treated for 3–107 months and the sum total follow-up duration was 1106.5 patient years. Overall, the cumulative incidence of skin masses, including all masses irrespective of diagnosis, did not differ significantly between the two groups (56.6% in the exposed and 58.3% in the non-exposed dogs) and the overall incidence rate for mass development did not vary (174 new cases/1000 patient years in the exposed dogs and 169 new cases/1000 patient years in the control dogs).