MON-440 Cyberknife Radiosurgery for Functional and Non-Functional Pituitary Adenomas: Long-Term Single-Center Experience

Background: In recent years, CyberKnife radiosurgery (CKRS) has become an accepted adjuvant treatment modality when surgery has failed to achieve biochemical control of functional pituitary adenomas or after subtotal removal of non-secretory and secretory adenomas. However, long-term experience and clinical follow-up is limited. We present a retrospective review of our institutional experience with CKRS in patients with functional and non-functional pituitary adenomas. Methods: Forty-eight patients (23M/25F, age range 24-83 years) with pituitary adenomas received CKRS. Median follow-up period was 50 months (range 1 to 123 months). Patients consisted of 31 with non-functioning adenomas, 10 with acromegaly, 5 with Cushing disease (CD) and 2 with prolactinomas. Changes in hormonal function and treatment complications were analyzed in each case. Results: The ranges of radiation doses administered and prescription isodose line were 2500-3500 cGy/5 fractions and 62-78%, respectively. Pituitary hormone secretion improved in all 17 functioning adenomas, with hormonal normalization observed in 11/17 (65%) patients over median of 14 months. In patients with nonfunctioning adenomas, 4/31 (13%) patients subsequently developed panhypopituitarism over a median duration of 16 months. Radiological data was available in 42 patients, and 11/42 (26%) patients had reduction in tumor size over median of 16.5 months, 4/42 (10%) patients had local tumor recurrence over median of 41.5 months, and 27/11 (64%) patients had stable and unchanged tumor size. Of those with local tumor recurrence, 1 patient that had CD was treated with a low dose of 2500 cGy of salvage radiation therapy, 1 patient had Crooke’s changes after a dose of 2500 cGy salvage surgery, and 2 patients had high MIB scores (> 10). Post-treatment complications included temporal radiation-induced changes (n=2), 6(th) nerve palsy (n=1), and secondary malignancy (n=1). No patients developed visual field deficits. Five- and 7-year local progression free survival rates were 90% and 83%, respectively. Four patients died due to the following reasons: suicide, unknown reason, previously diagnosed testicular malignancy and infield neuroendocrine malignancy. Conclusion: We describe the long-term efficacy, safety and complication profile of CKRS in the treatment of functional and non-functional pituitary adenomas in our cohort of patients. Our data demonstrated that CKRS is a safe and effective adjunct for salvage therapy in patients with pituitary adenomas that have failed first-line therapy. In functioning pituitary adenomas, hormone hypersecretion improved in all patients, with the majority of patients achieving biochemical remission. Post-radiosurgery pituitary hormone deficiencies resulting in panhypopituitarism was observed in only a minority of patients. Overall, local tumor control and survival rates were relatively high.