Investigation of efficacy of two different chemotherapy protocols used in neoadjuvant chemotherapy in clinical stages II–IV canine malignant mammary tumours

Abstract

The first aim of this study is to demonstrate the clinical efficacy and reliability of two different neoadjuvant chemotherapy (NAC) protocols consisting of doxorubicin/cyclophosphamide (AC) and paclitaxel in dogs with clinical stages II–IV canine malignant mammary tumours (CMTs). Secondly, to determine the Luminal A, Luminal B, HER2‐positive and triple‐negative molecular subtypes and their value in predicting clinical response to NAC in biopsy samples, and thirdly, to reveal the changes in Ki‐67, human epidermal growth factor receptor type 2 (HER2), oestrogen receptor (ER), and progesterone receptor (PgR) expression levels induced by NAC. Thirty dogs with clinical stages II‐IV CMTs (T1‐3N0‐1M0) according to the modified TNM system were included in the study. Dogs in group‐1 (n = 15) AC combination and dogs in group‐2 (n = 15) were administered paclitaxel. Partial response (PR) was the most common clinical response in both treatment groups (66.66% and 86.66%, respectively). There was no difference between the groups regarding clinical response parameters (p = .001). The rate of treatment responders was higher than the rate of non‐responders in both groups (p < .001). The adverse effects observed in both groups were mostly limited to grades 1 and 2 and all were easy to manage. The most frequently detected molecular subtype was Luminal A (59.25%). Complete response (CR) was achieved in 33.33% of dogs with triple‐negative CMT in the AC group and 14.29% of the Luminal A subtype in the paclitaxel group. Alterations in Ki‐67, HER2, ER, and PgR expressions after chemotherapy were not statistically significant (p > .05). As a result, we have shown that these neoadjuvant chemotherapy protocols are effective and safe alternative treatment options for CMTs.