Objectives The aim of this study was to evaluate the efficacy, long-term outcome and prognostic factors of feline squamous cell carcinoma (SCC) treated with photodynamic therapy (PDT). Methods Cats with histologically verified SCC of the head and neck received an intravenous injection of liposomal phosphorylated meta-tetra(hydroxylphenyl)chlorine (mTHPC) and 4 h later 652 nm light was delivered by a diode laser. One group received ⩽10 J/cm2, the other 20 J/cm2. Tumour response and duration were analysed with stage, tumour diameter, location and treatment intensity as prognostic factors. Results In total, 63 lesions in 38 cats underwent treatment with ⩽10 J/cm2 (n = 22) and 20 J/cm2 (n = 41). Overall response rate was 84% (complete remission 61%, partial remission 22%) with a mean progression-free interval of 35 months (median not reached) and a median overall survival time of 40 months (95% confidence interval 33–47). With regard to tumour stage, invasiveness yielded a highly significant worse outcome ( P <0.017). All patients with invasive tumours showed progression at less than 6 months. Larger lesions were associated with inferior control and treatment intensity, and tumour location did not influence response and duration. Conclusions and relevance PDT using a systemic photosensitiser leads to excellent long-term tumour control in the majority of cats. However, invasive and large tumours had a clearly inferior outcome, even if treated with the higher-dose intensity. This suggests that advanced lesions are not indications for PDT.
Long-Term Outcome and Prognostic Factors of Sporadic Colorectal Cancer in Young Patients
