Proton irradiation of feline nasal planum squamous cell carcinomas using an accelerated protocol

Fifteen cats were treated for squamous cell carcinoma of the nasal planum u sing proton beam radiation. The protocol used was accelerated with eight eq ual fractions given on four consecutive days, with a minimum of six hours b etween fractions. Total dose of radiation delivered was escalated with nine cats receiving 40.4 CGE (Co-60 Gy equivalent), and three cats each receivi ng 42.4 and 44.8 CGE. Complete response to the protocol was 60% (9/15), par tial response was 33% (5 of 15), and no response was seen in 6.6% (1 of 15) . Tumor control rate at one year was 64% and no cat had tumor recurrence af ter one year. Median survival was 946 days (+/- 516 days). Side effects wer e minimal with no severe reactions noted in the early or late period. This protocol offers an effective treatment for squamous cell carcinoma of the f eline nasal planum with minimal side effects and may be adaptable to conven tional radiation sources particularly when the field size is very small.