Efficacy and safety of CyberKnife radiosurgery for acromegaly

Acromegaly is a disease characterized by GH hypersecretion, and is typically caused by a pituitary somatotroph adenoma. The primary mode of therapy is surgery, and radiotherapy is utilized as an adjuvant strategy to treat persistent disease. The aim of this study was to determine the efficacy and tolerability of CyberKnife stereotactic radiosurgery in acromegaly.

A retrospective review of biochemical and imaging data for subjects with acromegaly treated with CyberKnife stereotactic radiosurgery between 1998 and 2005 at Stanford University Hospital.

Nine patients with active acromegaly were treated with radiosurgery using the CyberKnife (CK).

Biochemical response based on serum insulin-like growth factor-1 (IGF-1), anterior pituitary hormone function, and tumor size with MRI scans were analyzed.

After a mean follow up of 25.4 months (range, 6-53 months), CK radiosurgery resulted in complete biochemical remission in 4 (44.4%) subjects, and in biochemical control with the concomitant use of a somatostatin analog in an additional subject. Smaller tumor size was predictive of treatment success: baseline tumor volume was 1.28 cc (+/- 0.81, SD) vs. 3.93 cc (+/- 1.54) in subjects with a normal IGF-1 vs. those with persistent, active disease, respectively (P = 0.02). The mean biologically effective dose (BED) was higher in subjects who achieved a normal IGF-1 vs. those with persistent, active disease, 172 Gy(3) (+/-28) vs. 94 Gy(3) (+/-17), respectively (P < 0.01). At least one new anterior pituitary hormone deficiency was observed after CK in 3 (33%) patients: two developed hypogonadism, and one developed panhypopituitarism.

CK radiosurgery may be a valuable adjuvant therapy for the management of acromegaly.