AN ACCELERATED TECHNIQUE FOR IRRADIATION OF MALIGNANT CANINE NASAL AND PARANASAL SINUS TUMORS

Tumor and normal tissue response was assessed in 21 dogs with malignan t nasal tumors given 42 Gy cobalt radiation in 9 or 10 fractions over 11 to 13 days. Local tumor/clinical relapse recurred in 68% of dogs, w ith a median relapse free interval (RFI) of 270 days. Median survival was 428 days. One year survival for all dogs was 60%. RFI and survival times are better than, or similar to, previous reports of dogs treate d with radiotherapy only. Acute radiation effects were severe in one d og. Late effects were severe in six of 15 dogs (40%) with durable tumo r control. Late effects included bilateral blindness (3), osteoradione crosis (3), and seizures (1). These six dogs had a median survival of 705 days. Loss of vision occurred in at least one eye in nine dogs (47 %). Tumor staging based on CT findings was predictive for survival dur ation. Tumor histology was not predictive of outcome. Labrador Retriev ers were significantly over-represented. Despite comparable or improve d tumor control and survival times provided by this accelerated protoc ol, relative to other radiotherapy reports, local failure remains the major cause of death, and late radiation effects can be severe in dogs with durable tumor control.