Effect of anaesthesia on cell-mediated immunity in dogs undergoing mastectomy for mammary cancer

Abstract

Objective: To investigate if anaesthesia for canine cancer mastectomy further influences host cell-mediated immunity (CMI) promoting cancer progression.

Study design: A randomized, controlled, blinded clinical study.

Animals: A total of 20 bitches with malignant mammary tumours of clinical stage II or III undergoing the same type of mastectomy (regional mastectomy).

Methods: Dogs were randomly allocated to one of two anaesthetic groups (10 per group). The anaesthetic protocol of group A used minimally immunosuppressive drugs (tramadol, robenacoxib, propofol), whereas that of group B (control) used more immunosuppressive drugs (morphine, fentanyl, thiopental, isoflurane). For each animal, measurements of white blood cells (WBCs), neutrophils and lymphocytes, and flow cytometric assessment of T cells (CD3⁺), helper T cells (CD4⁺), cytotoxic T cells (CD8⁺) and CD5^low+ T cells were performed prior to anaesthesia (day 0) and on days 3 and 10 postsurgery. Data were analysed using a General Linear Model for repeated measures and presented as mean ± standard deviation, p ≤ 0.05.

Results: In all animals, on day 3, WBCs and neutrophils were significantly increased (p < 0.0005), while flow cytometry revealed significantly decreased relative percentages of T cells (CD3⁺) (p = 0.003) and their subpopulations CD4⁺ (p = 0.006), CD8⁺ (p = 0.029) and CD5^low+ (p = 0.031). Specifically, on day 3, the cytotoxic T cells (CD8⁺) were significantly decreased (p = 0.05) only in group B, whereas the CD4⁺ (p = 0.006) and CD5^low+ (p = 0.008) T cells in group A. The only significant difference between groups was found preoperatively in the CD4⁺/CD8⁺ ratio, which was higher in group A (p = 0.006).

Conclusions and clinical relevance: In dogs with mammary cancer undergoing regional mastectomy, a significant decrease in components of CMI was observed on day 3 postsurgery in both anaesthetic groups. Some indication, however, for better preserved cellular immunity by less immunosuppressive anaesthetic/analgesic drugs was detected, rendering their use advisable.

Keywords: anaesthesia; cell-mediated immunity; dog; immunosuppression; mammary cancer; mastectomy.