Radioactive Iodine Implants for Pan-invasive Pituitary Macroadenomas

Inclusion Criteria: * Pathological or radiographic diagnosis of a pan-invasive pituitary macroadenoma * Pan-invasive for the purposes of the protocol will be defined as meeting each of the following 2 major criteria: (1). tumor volume greater than 20 cc at enrollment, and (2). suprasellar extension. In addition, a pan-invasive tumor must meet any one of the following 3 minor criteria, a) unresectable tumor invasion into a cavernous sinus, b) bone or bone marrow invasion into the clivus or temporal bones, or c) tumor extension in any direction unlikely to be completely removed by specifically a transphenoidal surgical approach. * Patients who meet the two major criteria above (1 and 2) and are medically inoperable for tumor resection (due to confounding co-existing medical problems) are eligible without meeting any of the three minor criteria (a, b, or c). * Patients should be immediately threatened for vision loss or other significant neurological impairment directly related to tumor mass effect. As such, all patients enrolled would likely benefit from tumor response (shrinkage). * Patients must have visible tumor on imaging studies (MRI or CT) * The patient's Zubrod performance status must be 0-3. * Patients must be at least 18 years of age. * Mandatory Imaging Studies: Must be done 45 or fewer days prior to : MRI or CT scan of the brain including the entire skull base and all areas of tumor extension Exclusion Criteria: * Patients who are unable to undergo general anesthesia * Patients who are unable to undergo placement of a stereotactic head frame * Patients who are unable to provide informed consent * Patients who are pregnant or nursing * Patients with severe kidney dysfunction * Patients who have contraindications to MRI, such as implanted pacemaker device * Patients with diagnosis of pituitary carcinoma