Electrochemotherapy with carboplatin and bleomycin associated with mastectomy in cats with mammary carcinoma: A pilot study

In cats, the high incidence of malignant mammary neoplasms with elevated rates of metastasis and recurrence underscores the need for more effective therapies to prevent disease progression. This preliminary study evaluated the impact of carboplatin or bleomycin electrochemotherapy on recurrence rates, adverse effects, and overall survival in female cats with mammary carcinoma undergoing mastectomy. Thirty-four female cats with mammary carcinoma were assigned to four groups: Group 1 (mastectomy), Group 2 (mastectomy plus chemotherapy), Group 3 (mastectomy plus electrochemotherapy with carboplatin and chemotherapy), and Group 4 (mastectomy plus electrochemotherapy with bleomycin and chemotherapy). The tumors were classified and graded histologically, and the proliferative index was assessed using Ki-67. Most cases were stage III, and 50% had nodal metastases. The predominant tumor types included cribriform carcinoma and histological grade II. All groups showed a high Ki-67 proliferation index (>20%), with no significant differences (p = 0.753). Hematocrit values in the fourth chemotherapy session were higher in G3 than in G2 (p = 0.022). The highest numerical recurrence rate occurred in G1, while no recurrences were observed in G2 or G4 during follow-up; however, this difference did not reach statistical significance (p = 0.086). Overall survival analysis showed a 82% mortality rate; G1 had 100% mortality, with a significant difference compared with the other groups (p = 0.0287). More chemotherapy sessions (≥5) were significantly associated with increased overall survival (p = 0.002), adding a mean of 39.1 days to disease-free survival per additional session. Taken together, these preliminary findings suggest that mastectomy alone was insufficient to control progression the cancer. Carboplatin-based protocols, whether used as conventional chemotherapy or combined with electrochemotherapy, showed lower recurrence rates, fewer adverse effects, and longer overall survival. However, due to the limited sample size, these results should be interpreted with caution. Further studies with larger cohorts are warranted to confirm these observations.