The effect of naltrexone as a carboplatin chemotherapy-associated drug on the immune response, quality of life and survival of dogs with mammary carcinoma

Abstract

The objective of this study was to evaluate the effect of low-dose naltrexone (LDN) as a carboplatin chemotherapy-associated drug in female dogs with mammary carcinoma in benign mixed tumors (MC-BMT) after mastectomy and to assess its association with quality of life and survival rates. Sixty female dogs were included in this study, all of which had histopathological diagnosis of MC-BMT and were divided into three groups: G1 (control), consisting of animals submitted only to mastectomy with or without regional metastasis; G2, composed of treated animals that did not present with metastasis; and G3, treated dogs that presented with metastasis. G2 and G3 were also subdivided according to the treatment administered: chemotherapy alone (MC-BMT(-) C/MC-BMT(+) C) or LDN and chemotherapy (MC-BMT(-) C+LDN/MC-BMT(+) C+LDN). All animals were subjected to clinical evaluation, mastectomy, peripheral blood lymphocyte immunophenotyping, beta-endorphin and met-enkephalin quantification, and evaluation of survival rates and quality of life scores. The results showed higher serum concentrations of beta-endorphin and met-enkephalin, fewer chemotherapy-related side effects, and better quality of life and survival rates in the LDN-treated groups than in LDN-untreated groups (P < 0.05). Evaluation of clinical and pathological parameters indicated a significant association between the use of LDN and both prolonged survival and enhanced quality of life. These results indicate that LDN is a viable chemotherapy-associated treatment in female dogs with MC-BMT, maintaining their quality of life and prolonging survival rates.

Fig 1. Flow cytometry immunophenotyping of total T-lymphocytes, CD4+ and CD8+ T-lymphocytes, and CD4+/CD8+ T-cell ratio in peripheral blood of female dogs with MC-BMT.

Analysis is divided into before and after proposed treatment, subcategorized by the absence (-) or presence (+) of metastasis. Immunophenotypic analyses were performed using dual color flow cytometry as described in the Methods. Total lymphocytes were first selected based on their size (laser-forward scatter–FSC) and complexity (laser side scatter–SSC), and subsets were analyzed by quadrant statistics on FL1/FITC versus FL2/R-PE dot plots. Results are shown in a box plot format showing the minimum, median and maximum values of total T-lymphocytes. (A) CD4+ (B) and CD8+ T-lymphocytes (C) (expressed as a percentage of gated lymphocytes) and CD4+/CD8+ T-cell ratio (D) (expressed as a proportion). *Significant differences at p < 0.05, according to the Kruskal-Wallis test.

Fig 2. Beta-endorphin and met-enkephalin concentrations in the blood of female dogs with cancer as benign mixed tumors.

The results are divided into before and after the proposed treatment and subcategorized by the absence (-) or presence (+) of metastasis. Beta-endorphin concentrations for each sample (in pg/mL) were determined by ELISA (A). Met-enkephalin concentrations for each sample were determined by ELISA and calculated in ng/mL (B). *Significant differences at p < 0.05, according to the Kruskal-Wallis statistical test.

Fig 3. Representation of quality of life scores from female dogs with MC-BMT, before and after treatment with carboplatin, and in the presence of absence of LDN adjuvant treatment.

*Significant differences at p < 0.05, according to the Kruskal-Wallis statistical test.

Fig 4. Temporal analysis on quality of life scores over time from female dogs with MC-BMT.

Data are expressed as means of the quality of life scores for each group. *Significant differences between the LDN treated and LDN-not treated groups at p < 0.05. Statistical analysis was performed using a two-way ANOVA with post-hoc Tukey’s test.

Fig 5. Survival rates of animals with MC-BMT.

(A) Six-month survival curves of groups according to treatment (T) or not (NT) with LDN subgroups classified according to the absence (-) or presence (+) of lymph node metastasis (B and C). *Significant differences at p< 0.05 according to the Kaplan-Meier analysis.