Introduction

Canine tonsillar squamous cell carcinoma (TSCC) is an uncommon disease with an aggressive behaviour that carries a poor prognosis. This is a preliminary retrospective study of 20 cases. The primary objectives of this study were to establish if significant presenting clinical signs could be used as a prognostic guide and to compare the survival time of animals that received chemotherapy and radiotherapy with those that were only treated symptomatically. A secondary objective was to identify factors of potential prognostic significance that could be evaluated in a subsequent multicentre study.

Materials and Methods

Clinical records of dogs diagnosed with TSCC at Davies Veterinary Specialists between 2001 and 2006 were reviewed. Owners and referring veterinary surgeons were contacted by telephone for follow-up. Clinical signs, clinical stage, time of diagnosis, treatment and outcome were recorded. Data were analysed using the Kaplan-Meier, logrank and Cox's proportional hazards methods. Statistical significance was defined by p<0.05. Potential significance was defined by p<0.3.

Results

Dogs presented with a variety of clinical signs, the most frequent being enlarged lymph nodes (13/20), cough (8/20) and odynophagia (6/20); in 5/20 cases identification of the tumour was an incidental finding. Eleven dogs presented only with a primary tumour, 8/20 had lymph node spread and one had distant metastasis. Nine dogs received chemotherapy, four of which received adjuvant radiotherapy; one dog received radiotherapy only. The remaining dogs only received symptomatic treatment.

The median survival time (MST) for all patients was 151 days and ranged from 12 to 1268 days. Statistically significant covariates on univariate analysis included anorexia (p=0.0236), treatment with chemotherapy (p=0.0396) and treatment with radiotherapy (p=0.0276). Additional potentially significant variables included odynophagia, lethargy and dysphagia. On multivariate analysis only anorexia and chemotherapy remained statistically significant. Clinical stage at the time of presentation was not significantly associated with outcome.

Conclusions

Anorexia as a presenting clinical sign and the use of chemotherapy and/or radiotherapy were shown to be statistically significant prognostic factors in canine tonsillar squamous cell carcinoma. A plan has been made to broaden this study into a multicentre investigation examining the impact of all significant and potentially significant covariates.