Serum insulin concentration in dogs with insulinoma as a clinical marker for presence of metastasis at the time of diagnosis

BACKGROUND: Information regarding serum insulin concentration in dogs newly diagnosed with insulinoma and its association with clinical stage and survival time is lacking. OBJECTIVE: Examine association between serum insulin concentration and survival and clinical disease stage in dogs with insulinoma. ANIMALS. Fifty‐nine client‐owned dogs with a diagnosis of insulinoma from 2 referral hospitals. METHOD: Retrospective observational study. The χ (2) test was used to compare the proportion of dogs with increased insulin concentration in groups with or without metastasis at the time of diagnosis. Linear mixed‐effect models were built to compare differences in insulin concentration between dogs with and without evidence of metastasis at the time of original diagnosis. Cox's proportional hazards regression and Kaplan‐Meier graphs were used to evaluate the association between insulin concentration and insulin groups and survival. RESULTS: Median serum insulin concentration was 33 mIU/L (range, 8‐200 mIU/L) in dogs with World Health Organization (WHO) stage I disease and 45 mIU/L (range, 12‐213 mIU/L) in dogs with WHO stage II and III disease. No difference was found in the proportion of dogs with increased insulin concentration with or without metastasis (P = .09). No association was identified between insulin concentration and survival (P = .63), and between dogs grouped by insulin concentration and survival (P = .51). CONCLUSIONS AND CLINICAL IMPORTANCE: Serum insulin concentrations were not different between dogs with or without metastasis at diagnosis. The degree of insulinemia does not provide further information regarding the stage of the disease and is not associated with survival time in dogs with insulinoma.