Long-term results of gamma knife stereotactic radiosurgery for non-functioning pituitary adenomas

Abstract

Gamma Knife Stereotactic Radiosurgery (GK-SRS) is an established treatment for pituitary adenomas. In this retrospective review, we evaluate the long-term efficacy and safety of GK-SRS in the management of non-functioning pituitary adenomas. A total of 74 patients with non-functioning pituitary adenomas underwent GK-SRS at the University of Maryland between September 1992 and June 2003, and is the basis of this retrospective review. Of these, 65 patients (87.8%) had previously undergone resections by transsphenoidal or craniotomy approach. Patients who had previously external beam radiotherapy were excluded from this analysis. Median tumor size was 2.2 cm (range: 0.2–4.8 cm) before GK-SRS. The median prescription dose and isodose line were 14.0 Gy (range: 6–20 Gy) and 50% (range: 25–70%). The dose to the optic apparatus was limited to ≤8 Gy. The median and mean follow-ups for the entire cohort were 47.7 months and 55.9 months (range: 8.5–137.2 months), respectively; 25 patients (33.8%) were observed for more than 60 months. Tumor control was defined as no further growth, and was determined by serial MRIs in all patients. Tumor control after GK-SRS was successfully achieved in 98.6% (73/74) of patients. All tumors with cavernous sinus invasion and suprasellar extension were controlled. One person with a microadenoma progressed radiographically 12 months after GK-SRS and died one month later of an unrelated illness. Two patients developed worsening visual function after GK-SRS despite having excellent radiographic tumor responses. Before therapy both patients presented with significant visual dysfunction and were found to have tumor compression of the optic apparatus; visual function did not improve after resection and before GK-SRS. No patient with intact visual function before GK-SRS developed worsening vision, and no one developed a new endocrinopathy following GK-SRS. This study continues add to the body of literature supporting the use of GK-SRS in the management of patients with pituitary adenomas. The use of conformal technique to limit the optic apparatus dose to ≤8 Gy did not jeopardize the probability of achieving long-term tumor control. With a median follow-up of 4 years, our study demonstrates that GK-SRS is safe and highly effective in controlling non-functioning pituitary adenomas