Comparison of chemotherapy outcomes between normal and high serum cortisol concentration in dogs with lymphoma

Increased serum cortisol (COR) concentrations may induce glucocorticoid resistance by down-regulation of glucocorticoid receptor (GCR), resulting in decreased chemotherapy efficacy in dogs with lymphoma.

Investigate the relationship between serum COR concentrations and chemotherapy outcomes in dogs with lymphoma.

Thirty client-owned dogs with lymphoma, with serum COR concentration measured using serum samples collected at diagnosis.

Retrospective study. Dogs were divided into 2 groups based on serum COR concentrations: a normal group (n = 16) with COR concentrations <6 μg/dL and a high group (14) with COR concentrations ≥6 μg/dL. We compared signalment, clinical signs, stage, type of lymphoma, adrenal gland size, alkaline phosphatase (ALP) activity, response to chemotherapy, progression-free survival (PFS), overall survival (OS), and rate of P-glycoprotein (P-gp)- and GCR-positive cells between the 2 groups.

No significant differences were found in the demographic characteristics between the 2 groups. However, the high COR group exhibited a significantly lower response to chemotherapy, PFS, and OS compared with the normal COR group. Serum ALP activity was significantly higher in the high COR group than in the normal COR group. Adrenal gland size was also significantly larger in the high COR group. Although no significant differences were found in the rate of P-gp-positive cells between the 2 groups, the rate of GCR-positive cells was significantly lower in the high COR group.

Our data suggests that measurement of serum COR concentrations may serve as a potential prognostic factor and evaluation index.