Backgound:The Golden Retriever Lifetime Study (GRLS) is a prospective cohort of dogs within the contiguous United States, designed to investigate health of Golden Retrievers, with cancer as a research focus. Mast cell tumour (MCT) represents the most common skin malignancy in dogs. This is the first exploration of MCT epidemiology within the GRLS cohort, and the first epidemiologic report specific to MCT in the Golden Retriever breed.
Methods: MCT frequency was reported as proportion of the cohort, and incidence rate for first lifetime diagnosis. A lifetable was produced to assess incidence risk per year of age. The anatomical location, tissue origin and histopathologic grade of MCTs themselves were reported descriptively. Dogs with multiple MCT presentations or metastasis were further explored. Survival was compared between dogs with MCT and the remaining cohort, followed by a stratified analysis of time from first MCT diagnosis to death using Kaplan-Meier curves and the log-rank test.
Results: Within the cohort of 3,044 dogs, 164 (5.39%) dogs were diagnosed with 234 MCTs, corresponding to an incidence rate of 5.58 per 1,000 dog years at risk (95% confidence interval (95% CI): 4.76–6.51). Median overall lifespan was 11.68 years (95% CI: 11.25–12.33) in dogs diagnosed with MCT and 11.75 years (95% CI: 11.61–11.98) within the remaining cohort - with no statistically significant difference observed (log-rank test, p = 0.54). Regarding histologic grade, 47 of 234 tumours (20.09%) met the GRLS high-grade definition (with either Kiupel high or Patnaik grade 3 characteristics). De novo tumours were diagnosed in 26 dogs (15.85%), local recurrence occurred in 8 dogs (4.88%) and metastasis in 16 dogs (9.76%). Median survival time from first MCT diagnosis was 1,367 days (95% CI: 1200–1870) with only 11.59% (n = 19) having MCT recorded as cause of death. After stratification, survival was statistically significantly decreased in MCT cases where there was presence of local recurrence, presence of metastasis, or high histopathological grade (log-rank test, p < 0.05).
Conclusions: This epidemiological study reports age-specific frequency, clinical features and prognostic factors for Golden Retrievers with MCT. In this cohort, the lifespan of dogs with MCT diagnosis was not statistically significantly different from the remaining cohort.