Long-Term Outcome of Electrochemotherapy in the Treatment of Advanced Stages (T3-T4) of Feline Nasal Planum Squamous Cell Carcinoma.

Electrochemotherapy is increasingly used as a locoregional treatment for feline squamous cell carcinoma, but its role in advanced nasal planum disease remains poorly defined. This retrospective study evaluated the long-term outcome of ECT as a sole treatment modality in 18 cats with T3-T4N0M0 nasal planum squamous cell carcinoma. Adverse events were assessed according to VCOG-CTCAE v2. Response was assessed using RECIST v1.1 criteria, and progression-free survival (PFS), overall survival (OS) and time to progression (TTP) were analysed using Kaplan-Meier methods. At the end of treatment, 72.2% of cats achieved complete response, 16.7% partial response and 11.1% stable disease, resulting in an overall response rate of 88.8%. The 1-year complete response rate was 61.1%. Treatment response was significantly associated with PFS (p = 0.006), OS (p < 0.001) and TTP (p = 0.006), while recurrence was associated with shorter PFS (p = 0.003) and OS (p = 0.002). The 1-year risk of recurrence was 50%. Adverse events were mostly low-grade (VCOG Grade I-II) and self-limiting, the most common being transient local pain, erythema/crusting and pruritus; no grade ≥ 3 complications such as tissue necrosis or fistula formation were observed. These results suggest that ECT is an effective and well-tolerated treatment also in advanced stages nasal planum squamous cell carcinoma, with high response rates and long-term control disease. The risk of recurrence underscores the need for prolonged follow-up, as additional treatment sessions may be performed upon relapse, while ECT can also be used with palliative intent to prolong survival while preserving quality of life.