Stereotactic Radiosurgery XVI: A Treatment for Previously Irradiated Pituitary Adenomas

Abstract

We report the use of stereotactic radiosurgery delivered through an adapted linear accelerator [stereotactic multiple arc radiation therapy (SMART)] for pituitary adenomas not cured by conventional therapy. All 21 patients had undergone conventional radiotherapy (45-50 Gy); 18 had also undergone prior surgery. This cohort comprised 13 patients with somatotrope adenomas, four with corticotrope adenomas, one with a lactotrope adenoma, and three with nonfunctioning pituitary adenomas (median follow-up: 33 months, range: 3-72 months). SMART has proven effective, safe, and rapidly acting. We observed an accelerated reduction in GH and IGF-I levels in acromegaly, with normalization of GH and IGF-I levels in 58%. Mean GH fell from 21.1 mU/liter to 7.9 mU/liter (7 ng/ml to 2.6 ng/ml, P < 0.01, median 25 months) faster than our predicted fall to 50% at 2 yr with conventional radiotherapy. Mean IGF-I fell from 624 ng/ml to 384 ng/ml (P < 0.001). Tumor growth was controlled in two of three nonfunctioning pituitary adenomas, and three of four corticotrope adenomas. There were no adverse effects from SMART. Notably there have been no visual sequelae or further loss of anterior pituitary function in this heavily pretreated group. Our data indicate that SMART is an effective complementary therapy for pituitary adenomas that have displayed a suboptimal response to conventional therapy including external irradiation.

A systematic analysis of disease control in acromegaly treated with radiosurgery

“…1,7,8,10,16,19,22,23,[25][26][27][28]30,33,34,[37][38][39][40][41][42]45,[47][48][49]51 The mean reported patient age was 45.2 ± 3.78 years. The overall mean duration of reported follow-up was 48.5 ± 25.8 months, and the overall median duration of reported follow-up was a similar 46.6 ± 20.4 months.…”

“…Of these 951 patients, 472 (49.6%) achieved biochemical remission following SRS based on study-dependent endocrine criteria. 1,7,8,10,16,19,22,23,[25][26][27]30,[37][38][39][40][41][42]45,[47][48][49]51 When considering only those studies that used GH < 2.5 ng/ml or oral glucose tolerance test, GH < 1 ng/ml and normal IGF-I compared with age-and sexmatched controls as their criteria for biochemical remission, 44.5% of patients achieved disease control following SRS without medication. Utilizing a more stringent criteria of age-matched IGF-I normalization levels in series of 10 patients or more, our analysis revealed a similar 52.5% disease control rate in 506 patients with acromegaly treated using SRS.…”

“…Hormone normalization was achieved in 60.3% of patients when including those still on pharmacological therapies following SRS treatment. 1,8,23,30,37,[40][41][42]47,48 Pharmacological interventions before and/or after radiosurgery included both the shortand long-acting somatostatin agonists subcutaneous octreotide and octreotide-LAR or lanreotide, respectively, 30,42 the dopamine agonist cabergoline, 8,40 or the GH receptor antagonist pegvisomant. 30,42,48 Biochemical remission was defined as meeting study-specific endocrinological criteria for cure only while on 1 or more of the above-mentioned medications.…”

The role of stereotactic radiosurgery in the multimodal management of growth hormone–secreting pituitary adenomas

“…In fact, of the studies in our analysis in which a normal IGF-I level was the only criterion for hor-monal cure, the rates of endocrinological remission ranged from 20% to 71%. 18,20,36,48,60 As hormonal remission rates following radiosurgery were noted in 17% to 82% of patients in studies in which the more stringent criteria were applied, 2,4,5,14,16,21,33,[45][46][47]53,54,57,58 it appears that the definition of endocrinological remission is of variable consequence.…”

“…16 Using the aforementioned strict criteria for hormonal remission, the range of endocrinological normalization was 17% to 82%, and an additional 4% to 47% of patients achieved hormonal control following radiosurgery. 2,4,5,14,16,21,33,[45][46][47]53,54,57,58 For instance, Pollock et al 45 observed an endocrinological remission rate of 67% and Ikeda et al…”