Effects of Chemotherapy on Immune Responses in Dogs with Cancer

Abstract

Chemotherapy is assumed to be immunosuppressive; yet to the authors' knowledge, the effects of common chemotherapy protocols on adaptive immune responses in dogs with cancer have not been fully evaluated. Therefore, a study was conducted to evaluate the effects of 2 common chemotherapy protocols on T‐ and B‐cell numbers and humoral immune responses to de novo vaccination in dogs with cancer. Twenty‐one dogs with cancer (12 with lymphoma, 9 with osteosarcoma) were enrolled in a prospective study to assess effects of doxorubicin versus multi‐drug chemotherapy on adaptive immunity. Numbers of circulating T and B cells were assessed by flow cytometry, and antibody responses to de novo vaccination were assessed before, during, and after chemotherapy. The T‐ and B‐cell numbers before treatment also were compared with those of healthy, age‐matched, control dogs. Prior to treatment, dogs with cancer had significantly fewer (P < .05) CD4+ T cells and CD8+ T cells than did healthy dogs. Doxorubicin treatment did not cause a significant decrease in T‐ or B‐cell numbers, whereas treatment with combination chemotherapy caused a significant and persistent decrease in B‐cell numbers. Antibody titers after vaccination were not significantly different between control and chemotherapy‐treated dogs. These findings suggest that chemotherapy may have less impact on T‐cell numbers and ability to mount antibody responses in dogs with cancer than was previously anticipated, though dogs with lymphoma or osteosarcoma appear to be relatively T‐cell deficient before initiation of chemotherapy.