Objective: Single fraction stereotactic radiosurgery (SRS) is a common adjuvant therapy for hormonally active pituitary adenomas when surgical resection fails to control tumor growth or normalize hypersecretory activity. Marginal doses of 20-24 Gy are used at many centers and here we report our outcome data in patients treated with a higher marginal dose of 35 Gy.
Methods: Thirty-one patients with secretory pituitary adenomas (adrenocorticotropic hormone, n = 15; growth hormone, n = 13; prolactin, n = 2; thyroid-stimulating hormone, n = 1) were treated with 35 Gy to the 50% isodose line, and had a mean follow-up time of 40.2 months (range = 12-96). All patients were evaluated post-SRS for time to hormonal normalization, time to relapse, as well as incidence and time course of radiation-induced hypopituitarism and cranial neuropathies.
Results: Initial normalization of hypersecretion was achieved in 22 patients (70%) with a median time to remission of 17.7 months. After initial hormonal remission, 7 patients (32%) experienced an endocrine relapse, with a mean time to relapse of 21 months. New endocrine deficiency within any of the five major hormonal axes occurred in 10 patients (32%). One patient (3%) developed new-onset unilateral optic nerve pallor within the temporal field 3 years after SRS. Three patients (10%) reported transient new or increasing frontal headaches of unclear etiology following their procedures.
Conclusion: Time to endocrine remission was more rapid in patients treated with 35 Gy, as compared to previously reported literature using marginal doses of 20-24 Gy. Rates of endocrine remission and relapse, post-SRS hypopituitarism, and radiation-induced sequelae were not increased following higher dose treatment.
Keywords: 35 Gy; Gamma-knife surgery; Optic apparatus; Optic nerves; Pituitary adenoma; Stereotactic radiosurgery.
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