Endocrine Abstracts

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.

Design

This is a retrospective review of the biochemical and imaging characteristics for patients with active acromegaly treated with CK SRS at St.Bartholomew’s Hospital, between 2014–2019.

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 visit. Anterior pituitary hormone deficits were assessed before and after treatment. Tumour size was followed up with MRI.

Results

A total of 10 patients (7 male, mean age 36 years [± 12.6, SD]) with active acromegaly were treated with CK SRS, delivered as a single session. Nine patients were treated following failure to attain biochemical remission with transsphenoidal surgery (TSS). One patient had primary CK SRS, having declined TSS. Two patients had previously received conventional fractionated external beam radiotherapy. The median maximal tumour diameter preceding therapy was 6 mm (IQR 5.2–10.5 mm). Cavernous sinus invasion was reported in 2 cases. The median radiation dose prescribed was 23 Gy (IQR 20–24 Gy). At the time of treatment, 4 patients were on dopamine agonist, 4 patients on somatostatin analogue and 2 patients were on pegvisomant. The mean follow-up period was 31.6 months (± 13.5 months, SD). The 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. By the last follow-up visit, 5 patients required additional treatment, 2 patients had no change in treatment, 2 patients underwent dose reduction and 1 patient was off medication. The mean radiological follow-up using MRI was 16.6 months (± 15.9 months, SD). No cases showed tumour enlargement. Before treatment, 6 patients had evidence of anterior pituitary hormone deficits. One patient with pre-existing hypogonadism developed secondary hypothyroidism post-treatment. Side-effects included headache (7 patients), blurred vision (1 patient), fatigue and nausea (1 patient). Two patients reported no side-effects. There were no new visual fields defects, cranial nerve palsies, cerebrovascular events or secondary tumours.

Conclusion

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.