Gamma Knife Radiosurgery for Patients with Prolactin-Secreting Pituitary Adenomas

Abstract

To evaluate the efficacy of stereotactic radiosurgery (SRS) for patients with prolactin (PRL)-secreting pituitary adenomas that were refractory to medical management. Retrospective review of 22 patients treated with SRS from 1994 until 2006. All patients were either intolerant or their tumors were unresponsive to dopamine agonist therapy. Nine patients (41%) had undergone prior transsphenoidal surgery. The median serum PRL concentration before SRS was 88.4 ng/mL (range, 25-943). The median treatment volume was 2.2 cm(3) (range, 0.4-29.0); the median margin radiation dose was 25 Gy (range, 16-30). The median endocrinologic follow-up was 60 months (range, 16-129). Tumor control after SRS was 100%. Serum PRL concentration was significantly lower (median, 28.4 ng/mL) (P = 0.006) at last follow-up, but the 4-year actuarial rate of biochemical remission off medications was only 17%. No tested variable was associated with biochemical remission off medications. Overall, four patients (18%) had biochemical remission off medications and clinical improvement, three patients (14%) had normal serum PRL concentrations and clinical improvement on dopamine agonist therapy, seven patients (32%) had improved symptoms off medications but continued to have elevated serum PRL levels, and eight patients (36%) continued to be symptomatic with elevated PRL levels either on (n = 3) or off (n = 5) dopamine agonist therapy. The incidence of new anterior pituitary deficits was 42% at 4 years. SRS was effective in controlling tumor growth for patients with PRL-secreting pituitary adenomas, and the majority of patients were clinically improved.