Introduction: 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 hormonal normalization commonly occurs in about 50% of patients by 30 – 50 months. We report out outcome data for patients treated with a higher marginal dose of 35 Gy.
Methods: 31 patients with secretory pituitary adenomas (ACTH: n = 15, GH: n = 13, PRL: n = 2, TSH: n = 1) were treated with 35 Gy to the 50% isodose surface, with a mean follow-up of 39.2 months. All patients were evaluated post-SRS for time to normalization of hormonal secretion, time to relapse, and incidence of radiation-induced hypopituitarism and cranial neuropathies.
Results: Normalization of hypersecretion was achieved in 22 patients (70.1%) with a median time to remission of 17.7 months. There was 100% tumor control and 7 patients (31.8%) experienced an endocrine relapse, with a mean relapse time of 21 months. There was a small positive correlation between the percent of tumor receiving > 48 Gy and remission time (r = 0.28). New endocrine deficiency within any hormonal axis was observed in 10 patients (32.3%), with a mean time to any endocrine deficiency of 11.7 months. Three patients (9.7%) reported transient frontal headaches of unclear etiology following the procedure, with 1 of these patients (3.2%) reporting pain in a V1-V2 distribution.
Conclusions: Time to endocrine remission was more rapid in our patients treated with 35 Gy to the tumor margin when compared to the 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 when using the higher dose treatment.
Patient Care: SRS at higher doses will allow patients to have faster remission rates, reduce symptoms, and permit discontinuation of anti-pituitary medications earlier. This in turn greatly improves quality of life of our patients.
Learning Objectives: Stereotactic gamma-knife radiation for secreting pituitary adenomas can be given at higher doses, with faster remission rates without an increase in morbidity.