Long-term outcome of eight cats with non-lymphoproliferative nasal tumours treated by megavoltage radiotherapy

A retrospective study was undertaken to evaluate the long term survival of eight cats with non-lymphoproliferative nasal tumours treated by megavoltage radiotherapy alone. Adenocarcinoma was the most commonly diagnosed tumour. Megavoltage radiotherapy was given to eight cats in 4-6 fractions of 4-8 Gys over a 16 to 28 day period. Seven cats completed the radiotherapy schedule and only two cases developed mild acute radiotherapy side effects. Median survival time after the completion of the radiotherapy course as calculated by Kaplan-Meier survival analysis was 382 days. The 1 year survival rate was 63%. All cats were euthanased because of either a poor response to radiotherapy or recurrence of the nasal tumour. This study demonstrates that a coarse fractionation regime of megavoltage radiotherapy can provide effective long-term palliative treatment for feline nasal tumours. The coarse fractionation schedule has the advantages of requiring only four to six treatments.