Stereotactic radiation treatment of a pituitary mass in a rabbit

A 9-year-old female spayed Holland Lop rabbit (Oryctolagus cuniculus) presented with abnormal eyelid positioning on the right eye of 2 week duration. A full neurological examination revealed ptosis, enopthalmia, decreased palpebral reflex of the right eye. A pre and post contrast CT-study confirmed a large heterogeneously contrast-enhancing and partially peripherally mineralized parasellar pituitary mass. Stereotactic radiation was performed delivering 3 fractions of 8 Gy every other day (total dose 24 Gy) using volumetric-modulated arc therapy for the pituitary mass. A progressive decrease in size of the pituitary mass was observed on two follow-up CT-studies at six- and eighteen-months post-radiotherapy. The adrenal panels performed during follow-up visits suggested increased adrenal activity post-radiotherapy. No adverse effects of radiation therapy were noted at home or subsequent veterinary visits. CT imaging was a reliable modality for diagnosing and monitoringthe pituitary mass. Treatment with stereotactic radiotherapy resulted in a marked reduction in the pituitary mass volume with a long survival time and without adverse effects. Radiation therapy should be considered a treatment option in rabbits with pituitary tumors and the protocol used in this case could be used as a reference for future cases.