At the University of Virginia, 342 patients with pituitary lesions were treated with the Gamma Knife radiosurgery. Patients with a secretory adenoma included 85 patients with acromegaly, 65 patients with CD, 28 patients with a prolactinoma, and 23 patients with Nelson's syndrome. Because Gamma Knife treatment is not expected to be effective immediately, analysis of the effect of treatment was confined to patients with acromegaly followed 18 mo or more after treatment (conventional radiation is rarely effective before 3-5 yr after treatment). In patients with CD, a prolactinoma, or Nelson's syndrome, patients were considered evaluable 12 mo after treatment or if remission occurred within 12 mo of treatment. These times for evaluation are arbitrary but are based on comparison with the results of conventional fractionated pituitary radiation to provide a reasonable comparison of the results of both techniques. Because most of the patients do not reside in the immediate area, obtaining follow-up information is sometimes problematic. Thus, necessary information on some patients is lacking. If there was no follow-up information on these patients, they were excluded from analysis. When possible, follow-up information was obtained from visits to the Pituitary Clinic at the University of Virginia, contact with the referring physician, or contact with the patient.
Eighty-five patients were treated and 58 were considered evaluable (followed >18 mo or remission before 18 mo). Serum IGF-1 became normal in 17 of 58 patients (29%) between 5 and 98 mo after treatment; the mean time to remission was 27 mo. A new hormone deficiency developed in 17 of 58 patients (29%). No patient who achieved remission had a subsequent serum IGF-1 increase; one patient was given a second Gamma Knife treatment 5 yr after the first treatment. There was no difference in the radiation dose between patients who achieved remission and those who did not achieved a normal serum IGF-1 concentration. One patient died of unknown cause during the follow-up period.
Sixty-five patients were treated and 42 were evaluable (followed >12 mo or remission before 12 mo). A normal 24-h UFC measurement was achieved in 31 of 43 patients (74%); this occurred within 2 to 62 mo after treatment. The mean time to remission was 16 mo. A new hormone deficiency developed in 10 of 42 patients (24%). Two patients in remission subsequently developed elevated 24-h UFC levels and underwent a second Gamma Knife treatment. One patient had deterioration of vision; this patient had not received prior conventional radiation therapy. Three patients in this group died, one of progressive CD, one from a myocardial infarction, and one from sepsis. There was no difference in the total radiation dose administered to patients who achieved remission and those who did not achieve remission.
Twenty-eight patients with a PRL secreting adenoma received Gamma Knife therapy. These were patients who did not respond to medical therapy with a dopamine agonist and who underwent pituitary surgery to reduce tumor mass. Fifteen patients were considered evaluable (followed >12 mo). A normal serum PRL occurred in 4 of 15 patients (26%). Remission occurred at 18 to 51 mo after treatment; the mean time to remission was 30 mo. A new hormone deficiency occurred in 5 patients (33%). Three patients died, two from progressive disease and one from a myocardial infarction. No patient who achieved remission had a relapse.
There were 23 patients with Nelson's syndrome treated. Sixteen were evaluable (followed >12 mo). A normal serum ACTH concentration occurred in one patient (6%). A new hormone deficiency developed in 3 of16 patients (19%). Three patients in this group of 23 died, two of progressive disease and the one of unknown cause.
Pituitary radiation, regardless of delivery method, does not produce an immediate cure or reduction in tumor volume. Thus, it should be used as adjunctive therapy with the goal of controling tumor growth and excessive hormone production to prevent the complications and risk of premature mortality associated with hypersecretory states. Most of these patients have not been successfully treated with other modalities, including surgery and medical therapies, and radiation treatment is employed in the most difficult of circumstances.
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