PHOTODYNAMIC THERAPY RESPONSE IN CATS WITH CUTANEOUS SQUAMOUS-CELL CARCINOMA AS A FUNCTION OF FLUENCE

The response of advanced stage cutaneous squamous cell carcinomas (SCC ) following treatment with photodynamic therapy (PDT) has been poor. I t was the aim of this pilot study to determine whether an increase in the delivered fluence (i.e, energy density) would improve the duration of tumour remission in cats with advanced-stage SCC. Tumours were tre ated with aluminium phthalocyanine tetrasulphonate (AlPcS4) PDT at a f luence of either 100 J cm(-2) or 200 J cm(-2) and tumour response was evaluated at regular intervals. Those feline tumours treated with a fl uence of 100 J cm(-2) (n = 8) had a significantly shorter median remis sion duration (69 days; range 0-619 days) than those feline tumours tr eated with 200 J cm(-2) (n = 6; 522 days; range 151-1057 days). It is our conclusion that a fluence of 200 J cm(-2) is well tolerated and mo re effective when treating cats with advanced stage cutaneous SCC.