3D conformal radiation therapy for palliative treatment of canine nasal tumors.

We evaluated the response of 38 dogs treated with a coarsely fractionated, palliative radiation protocol based on CT-based 3D treatment planning. Dogs with histologically confirmed malignant nasal tumors were studied. Treatment prescriptions consisted of 3-4 x 8 Gy, 4-5 x 6 Gy, or 10 x 3 Gy fractions. Selected patient and tumor factors were evaluated for an effect on outcome. Resolution of clinical signs was reported after irradiation in all dogs. Acute toxicities were mild and short lived. Thirty-seven of 38 dogs died or were euthanized due to tumor-related disease. Overall median progression-free interval (PFI) was 10 months. Tumor stage affected response, with modified stage 1 patients having a median PFI 21.3 months vs. a median PFI of 8.5 months for modified stage 2 patients (P = 0.0006). Modified stage was the only factor significantly related to outcome. Based on these findings, a palliative radiation prescription based on computerized treatment planning may be justified in some canine nasal tumor patients.