Linear-accelerator-based modified radiosurgical treatment of pituitary tumors in cats: 11 cases (1997-2008).

Determine the efficacy and safety of a linear-accelerator-based single fraction radiosurgical approach to the treatment of pituitary tumors in cats. Retrospective study. Eleven client-owned cats referred for treatment of pituitary tumors causing neurological signs, or poorly controlled diabetes mellitus (DM) secondary either to acromegaly or pituitary-dependent hyperadrenocortism. Cats underwent magnetic resonance imaging (MRI) of the brain to manually plan radiation therapy. After MRI, modified radiosurgery was performed by delivering a single large dose (15 or 20 Gy) of radiation while arcing a linear-accelerator-generated radiation beam around the cat's head with the pituitary mass at the center of the beam. Eight cats were treated once, 2 cats were treated twice, and 1 cat received 3 treatments. Treated cats were evaluated for improvement in endocrine function or resolution of neurological disease by review of medical records or contact with referring veterinarians and owners. Improvement in clinical signs occurred in 7/11 (63.6%) of treated cats. Five of 9 cats with poorly regulated DM had improved insulin responses, and 2/2 cats with neurological signs had clinical improvement. There were no confirmed acute or late adverse radiation effects. The overall median survival was 25 months (range, 1-60), and 3 cats were still alive. Single fraction modified radiosurgery is a safe and effective approach to the treatment of pituitary tumors in cats.