Endocrine Response after Gamma Knife-Based Stereotactic Radiosurgery for Secretory Pituitary Adenoma

Purpose: To examine treatment outcomes of Gamma Knife-based stereotactic radiosurgery (GK-based SRS) for secretory pituitary adenomas. Materials and Methods: 25 patients were treated with GK-based SRS for secretory pituitary adenomas with ≧12 months of follow-up. Results: For prolactinomas, 2 of 4 patients (50%) showed normalization of serum prolactin at a mean time of 18 months. One of 4 had a ≧50% decrease but still abnormal prolactin levels. For adrenocorticotrophic hormone-secreting tumors, 6 of 12 patients (50%) showed normalization of their endocrine levels at a median of 10 months. An additional 2 (17%) had a ≧50% decrease. For growth hormone-secreting tumors, 4 of 9 patients (44%) showed normalization of endocrine levels at a median time of 30 months. Two patients (22%) had ≧50% lower but abnormal endocrine levels. Conclusion: GK-based SRS provides a reasonable rate of endocrine normalization of secretory pituitary adenoma. The time to endocrine response is shorter than reported for fractionated external beam radiotherapy. There is a low risk of optic neuropathy.