Uso da eletroquimioterapia em gatas com neoplasias mamárias submetidas à mastectomia

Abstract

In felines, the high incidence of malignant mammary neoplasms, coupled with elevated rates of recurrence and metastasis, underscores the need for more effective therapies to delay or impede disease progression. This study aimed to evaluate the feasibility and impact of electrochemotherapy (ECT) with carboplatin, applied to the surgical bed after mastectomy, followed by adjuvant chemotherapy, on recurrence and metastasis rates, the frequency of adverse events associated with chemotherapy, and the survival rate of queens with mammary carcinoma. A total of 34 queens with mammary neoplasms participated, divided into four groups: Group 1 (G1) – mastectomy only (n=11); Group 2 (G2) – mastectomy followed by adjuvant chemotherapy (CT) (n=11); Group 3 (G3) – mastectomy, ECT with carboplatin, and adjuvant CT (n=6); and Group 4 (G4) – mastectomy, ECT with bleomycin, and adjuvant CT (n=6). Post-surgery, the patients were clinically monitored to identify recurrences/metastases, analyze the frequency of adverse events, and determine survival rates. Clinical staging was performed, and tumors were histologically classified, graded, and assessed for cell proliferation rate (Ki-67). Most patients were in stage III, with lymph node metastasis present in more than 50% of cases. The most common histological subtype was grade II cribriform carcinoma. High cell proliferation was observed in all groups (Ki-67 > 20%), with no statistically significant differences (p=0.086). Group G3 showed a significantly elevated hematocrit in the fourth chemotherapy session (p=0.03). Metabolic, gastrointestinal, and respiratory adverse events did not differ among the groups treated with chemotherapy, regardless of the use of electrochemotherapy. The recurrence rate was highest in G1 (54.5%), whereas G4 had no cases to date. Disease-free survival increased by 39.4 days/session with chemotherapy, regardless of the use of electrochemotherapy or the chemotherapeutic agent used (p = 0.002; R² = 0.23). The overall mortality rate was 82.35% (28/34), with 100% in G1. Survival analysis indicated a significant difference between G1 and G2 (p=0.005), suggesting that chemotherapy provides better disease control. In conclusion, mastectomy alone is insufficient to control malignant mammary tumors in queens. Chemotherapy with carboplatin proved to be a viable therapeutic option, showing positive results regarding laboratory parameters and survival. Protocols combining mastectomy, electrochemotherapy with carboplatin or bleomycin, followed by 9 adjuvant CT, have proven safe for application in queens with breast cancer. However, the complete efficacy of ECT cannot yet be determined due to the limited sample size. Despite this, its application to the surgical bed may be beneficial in delaying or preventing regional recurrences and metastases, especially in smaller mammary tumors.