Published results can be found here.

Study Start Date: 01/01/2008
Study End Date: 12/31/2008

Radiosurgery Treatment for Cats with Pituitary Tumors: A Pilot Study

Acromegaly and pituitary-dependent hyperadrenocorticism (PDH) are endocrine diseases of cats resulting from the presence of a tumor in the pituitary gland. Both disorders are important as they cause debilitating clinical disease, with relatively high mortality rates. The medical and surgical options for management of feline PDH and acromegaly are currently limited and associated with significant complications, and this may lead to under diagnosis of these disorders.

Radiosurgery, also known as stereotactic radiation therapy, is an exciting new technology that uses a state-of-the-art linear accelerator to deliver radiation to a specific area while minimizing the dose to normal surrounding tissues. No actual surgery is involved, but the name is used because the radiation can ablate a tumor as precisely as surgery, but without disruption of surrounding tissues. This technique is a standard treatment for pituitary tumors in human patients, however up until this time radiosurgery capabilities were limited to human facilities.

Colorado State University recently purchased a TrilogyT radiation therapy unit specifically to make radiosurgery available to veterinary patients. The objectives of this study are to establish an efficacious treatment protocol for pituitary ablation by radiosurgery, to determine if there is resolution of endocrine disease after radiosurgery in cats with pituitary tumors, and to determine the effects of radiosurgery on pituitary function.

Cats that have a pituitary tumor identified by computed tomography or magnetic resonance imaging, together with signs of endocrine disease, will be enrolled in the study. Patients will receive radiosurgery, with endocrine testing, clinical evaluation, and computed tomography before and after therapy.

Study Design:
Prospective case series

Sample Size:
6 cats

Inclusion criteria:
Demonstration of a pituitary tumor by CT or MRI, with clinical signs of endocrine disease associated with the tumor. Before entry into the study, all patients must receive a diagnostic evaluation that includes a complete blood count, serum chemistry profile, urinalysis, urine culture, abdominal ultrasound and thoracic radiographs. Echocardiography will be required for patients with signs of cardiac disease. On entry to the study, patients will receive a physical examination, ophthalmologic examination, blood pressure measurement and review of test results. Additional testing provided by the study will include an ACTH stimulation test, a thyroid panel, endogenous ACTH levels, and serum IGF-1 levels. These tests will be performed prior to radiosurgery, and will be repeated at 2, 6, 12, 26 and 52 weeks after completion of the radiosurgery, in order to monitor pituitary function over a long period. For consistency of interpretation, all endocrine testing will be performed at Michigan State University (MSU). Testing may be performed by the primary care veterinarian, but must be submitted to MSU, and the results will be communicated to the study investigators.

Exclusion Criteria:

1. Other significant concurrent disease.
2. Disease that precludes anesthesia.
3. Inability for the cat to be presented to CSU for radiation surgery.

Study Controls:
No controls - it is a case series.

Study Endpoint(s):
Patients will receive radiosurgery therapy and then be followed for one year.

Samples:
Affected cats should be referred to CSU for evaluation and treatment. After therapy, follow-up diagnostic testing can be performed by the primary care veterinarian, but must be submitted to MSU and the results sent to CSU.

Costs/Reimbursements:
Clients will receive $1000 towards the cost of the radiosurgery. The follow-up CT will be performed at CSU at no charge. The study will pay for endocrine testing prior to radiosurgery, and 2, 6, 12, 26, and 52 weeks after radiosurgery.

Full Disclosure information:

• The study is funded by an intramural grant from CSU.
• The investigators do not have any conflict of interest.
• The study will be published if results are negative.
• The study will be reported on VIN.
• The authors will acknowledge VIN if the study is published.