Alterations in Erythrocyte and Platelet Characteristics Are Poor Indicators of Metastasis in Dogs with Carcinoma or Sarcoma: A Preliminary Study

Cancer is a leading cause of death in humans and dogs. Several erythrocyte and platelet characteristics (indices and morphology) have shown promise as indicators of metastasis in humans. Similar studies have not been performed in dogs. This study evaluated erythrocyte and platelet characteristics measured on the Advia 2120i in 59 tumor-bearing dogs with carcinoma or sarcoma. Tumor-bearing dogs with and without intracavitary hemorrhage that underwent complete post-mortem and histopathology examinations were compared to healthy age-controlled dogs. Carcinoma- and sarcoma-bearing dogs without hemorrhage were compared. All tumor-bearing dogs without hemorrhage or metastasis were compared to those with metastasis, and characteristics were evaluated as indicators of metastasis. Tumor-bearing dogs without intracavitary hemorrhage (n = 49) had decreased hematocrit (p = 0.002) and reticulocyte hemoglobin content (p = 0.022), and increase in anisocytosis (p = 0.002), polychromasia (p = 0.002), macrocytosis (p = 0.032), codocytes (p = 0.022), absolute reticulocyte count (p = 0.035), platelet concentration (p = 0.002), plateletcrit (p = 0.022), and platelet volume distribution width (p = 0.022) compared to healthy dogs (n = 20). In tumor-bearing dogs with intracavitary hemorrhage (n = 10), additional significant differences were reflective of acute hemorrhage. No difference in characteristics between carcinoma- and sarcoma-bearing dogs without hemorrhage was identified. After correction for multiple comparisons, no differences in erythrocyte or platelet characteristics were identified between tumor-bearing dogs without intracavitary hemorrhage and metastasis and those without metastasis. Significant differences in characteristics exist between tumor-bearing dogs and healthy dogs. Based on the limited number of dogs in this preliminary study, no red blood cell or platelet characteristics were associated with metastatic disease in tumor-bearing dogs without hemorrhage.