Temozolomide in Treating Patients With Invasive Pituitary Tumors

DISEASE CHARACTERISTICS: * Clinically demonstrable invasive pituitary macroadenoma, including any of the following subtypes: * Growth hormone-secreting * Prolactin-secreting * Adrenocorticotrophic hormone-secreting * Non-secreting * Must have biochemical evidence of any of the following: * Acromegaly as measured by serum insulin-like growth factor-1 (IGF-1) * Prolactinoma as measured by serum prolactin (PRL) * Cushing's disease as measured by 24-hour urinary-free cortisol * Inadequate tumor control, defined as a visible pituitary tumor ≥ 1 cm in maximal diameter encasing the carotid arteries, and/or invading into the cavernous sinuses, and/or abutting/invading the optic chiasma as demonstrated by MRI scan with or without contrast * Previously assessed by radiosurgery and meets ≥ 1 of the following criteria: * Not a suitable candidate for radiotherapy (e.g., tumor abutting and/or invading the optic chiasm) * Declined radiotherapy (in light of side effects or personal choice) * Has not exhibited tumor shrinkage or tumor continues to grow ≥ 1 year after completion of radiotherapy * Must have a normal visual field evaluation by Goldman perimetry * No visual field abnormalities * Hypopituitarism allowed as evidenced by any or all of the following: * Subnormal growth hormone response to arginine/growth hormone-releasing hormone testing (normal response is an increase of \> 4 ng/mL) * Low age- and sex-matched IGF-1 levels * Low thyroid-stimulating h…