Endocrine Abstracts

Background: Gamma-Knife Stereotactic Radiosurgery (STRS) is a single highly focused dose of radiotherapy used for intracranial pathologies, including pituitary tumours. At the National Centre for Stereotactic Radiosurgery in Sheffield more than 450 patients undergo STRS per year. The UK experience of this modality of treatment for acromegaly is limited because of the few gamma knife units in operation.

Objective: To assess the effectiveness and safety of gamma-knife stereotactic radiosurgery (STRS) in the management of acromegaly.

Patients: From 1994-2001 twenty-seven patients with acromegaly were treated in Sheffield. Of these, full follow-up data was available on 20: 15 male, 5 female, mean age 47y (range 31-65). 16/20 had undergone previous transsphenoidal (TpS) surgery alone; 2 where treated as primary therapy; 3 had TpS and fractionated 3 field radiotherapy (RT); one had TpS, craniotomy and RT.

Treatment: All patients were treated to the 50% isodose, median marginal dose 25 Gy, range 19-35. The dose to the optic chiasm was <8Gy in all.

Results: Mean follow-up (FU) was 4.2y (range 2-9y). 15/20 were assessed with IGF1: at 2y FU mean IGF1 had fallen in all patients from 620 (± 243 SD) to 412 (± 153 SD) p=0.0002. At the final follow-up IGF1 fell in all patients to a mean of 341 (± 202 SD) (54% of pre STRS) p<0.0001. At 5.5y FU 8/20 (40%) had 'safe' levels of GH or IGF1 within the age adjusted normal range. Tumour size remained constant in 10 patients, decreased in 8, and in 2 the rate of growth slowed. New hormone deficiency developed in only patient (TpS alone previously).at 3.5y of FU

Conclusions: This is the largest reported UK series of acromegaly treated with STRS, which appears effective and safe and has a low incidence new pituitary dysfunction, but longer-term follow-up is needed to fully assess this.