Efficacy and Safety of CyberKnife Stereotactic Radiosurgery in Acromegaly

Abstract

Abstract Aims Objective: Active acromegaly is associated with increased mortality. While surgery is the mainstay of treatment, it is not always curative. In selected cases, CyberKnife stereotactic radiosurgery (CK SRS) can be used as adjuvant treatment in patients with persistent disease. Method Methodology: Biochemical response was measured using serum IGF-1 levels, calculated as a percentage of the upper limit of normal (% ULN). Levels were recorded prior to treatment, at 6-12 months post-treatment and at the most recent follow-up. Anterior pituitary hormone deficits were assessed before and after treatment. Tumour size was followed-up using MRI. Results 10 patients (7 male, mean age 36 yrs [+/- 12.6, SD]) with acromegaly were treated with CK SRS. 9 were treated following failure to attain biochemical remission with TSS. 1 had primary CK SRS. 2 had previous conventional fractionated external beam radiotherapy. Median tumour diameter was 6 mm (IQR 5.2-10.5 mm), with cavernous sinus invasion in 2 cases. The dose was 20-24Gy/1#. 4 patients were on dopamine agonist, 4 on somatostatin analogue and 2 on pegvisomant. Mean follow-up 31.6 months (+/- 13.5 months, SD). Median IGF-1 % ULN was 146% pre-treatment (IQR 126.5-208.5), 109% at 6-12 months (IQR 76.5-131%) and 71% (IQR 59-91%) at last follow-up. Mean radiological follow-up 16.6 months (+/- 15.9 months, SD). No cases showed tumour enlargement. One patient developed secondary hypothyroidism. Side-effects: headache (7 patients), blurred vision (1 patient), fatigue/nausea (1 patient). No new visual fields defects, cranial nerve palsies, cerebrovascular events or secondary tumours. Conclusion Conclusions: CK SRS appears safe and effective in selected patients with acromegaly, when there is failure to attain biochemical cure with surgery and in patients intolerant or resistant to medical treatment.