Henry Cloete¹, Alan Radford¹, Cassandra Raby², Holly Blackburn³, David Killick¹, P-J Noble¹, Gina Pinchbeck¹, David Singleton^1,4, Marisol Collins¹

¹University of Liverpool, Liverpool, United Kingdom. ²University of Leeds, Leeds, United Kingdom. ³Rainbow Equine Hospital, York, United Kingdom. ⁴IVC Evidensia, Bristol, United Kingdom

Objectives

Feline Injection Site Sarcomas (FISS) are aggressive neoplasms which typically grow rapidly at previous injection sites. This study aimed to assess specific risk factors associated with the development of strongly suspected cases of FISS identified within electronic health records from a network of UK primary care veterinary practices partaking in the Small Animal Veterinary Surveillance Network (SAVSNET).

Methods

A regular expression (regex) was designed to identify consultations containing terminology suggestive of injection site sarcomas (ISS) between March 2014 and November 2024. Records identified through this automated search were subsequently reviewed manually. Only consultations in which the attending veterinary surgeon confirmed, or strongly suspected FISS were retained for analysis.

Results

From an initial 11,514,566 electronic health records, this process identified 3958 consultations with terminology relevant to ISS, 76 were related to confirmed or strongly suspected ISS, involving 74 cats and 2 dogs. For feline cases, potential risk factors were evaluated using multivariable regression modelling, with matched controls. Vaccination with core vaccines alone was not a significant predictor of odds of suspected FISS development (OR 1.58, 95% CI 0.79-3.13, p=0.189), exposure to feline leukaemia virus (FeLV) vaccines however were (OR 2.34, 95% CI 1.33-4.14, p=0.003). Age was also identified as a significant predictor of suspected FISS, with increasing age associated with a higher predicted probability of disease. The median age of affected cats was 12.2 years (IQR 10.1-15).

Statement: Impact/ Clinical Significance

These findings provide insight into risk factors associated with suspected FISS within a primary care population and may help inform vaccination discussions and risk communication in practice.