The aim is to demonstrate the clinical efficacy and safety of two different neoadjuvant chemotherapy protocols consisting of anthracycline /cyclophosphamide(A/C) combination and paclitaxel in dogs with locally advanced mammary tumors, subtype determination according to Ki67, HER2, estrogen and progesterone biomarkers in biopsy samples taken before neoadjuvant chemotherapy, to determine the prognostic value of these subtypes in predicting clinical response to neoadjuvant chemotherapy and to evaluate the immunohistochemically comparative changes ofneoadjuvant chemotherapy on these biomarkers in mammary tissues taken after the operation. 

In the study, 30 dogs which has advanced stage mammary tumor randomly dividedinto two groups, Neoadjuvant A/C combination  was used in one of the groups as anthracycline 25-30 mg/m2 and cyclophosphamide 100 mg/m2 in the form of i.v. slow injection with an interval of 3 weeks for 4 cures, while the other group was given paclitaxel chemotherapy as 60mg/m2 i.v. slow injection once a week for 12 weeks. Changes in Ki67, HER-2, estrogen and progesterone biomarkers were investigated immunohistochemically in tumor tissues taken 4 weeks after the end of chemotherapy. 3/15 (20%) Complete Response(CR), 10/15 (66.66%) Partial Response(PR),1/15 (6.66%) Stable Disease(SD) and Progressive Disease(PD) were determined in dogs treated with A/C chemotherapy. PR was observed in 13/15 (86.66%) of dogs receiving paclitaxel chemotherapy, CR and PD in 1/15 (6.66%). In both groups, the rate of those who responded to treatment was found to be statistically significant compared to the rate of those who did not respond to treatment. Subtypes of CMTs were determined based on this biomarkers in biopsy samples taken before neoadjuvant chemotherapy. The excess of luminal type A breast tumor was found as statistically significant. In the A/C group, the percentage of complete response in the triple-negative subtype was higher than the others. Changes in biomarkers before and after treatment were not statistically significant. 

As a result, it was found that the use of neoadjuvant chemotherapy protocols is an  alternative treatment option to the effective, reliable and up-to-date treatment approach at the applied dose and range.