Context: Single-session stereotactic radiotherapy (SR) may be a potential adjuvant treatment in acromegaly.

Objective: We analyzed the safety and efficacy of SR in patients who had previously received maximal surgical debulking at our centre.

Design: Retrospective analysis of hormonal, radiological, and ophthalmologic data collected in a predefined protocol from 1994 through 2006.

Setting: The study was performed at a university hospital.

Patients: Eighty-three acromegalic patients, 52 women and 31 men, with a mean age of 42.6 ± 1.2 yr. The median follow-up was 69 months (IQR, 44 to 107 months).

Intervention: The patients were treated with SR for residual or recurrent GH-secreting adenoma.

Main Outcome measure: Normalization of age- and sex-adjusted IGF-I levels together with a basal GH level below 2.5 µg/liter without concomitant GH-suppressive drugs.

Results: Fifty patients (60.2%) reached the main outcome of the study. The rate of remission was 52.6% at 5 yr (95% C.I., 40.6 - 64.6%). Other 13 patients (15.7%), who were resistant to somatostatin analogs, were in remission after SR. Multivariate analysis showed that low basal GH and IGF-I levels were associated with a favorable outcome. No serious side effects occurred after SR. The 5-yr cumulative risk of new onset hypogonadism, hypothyroidism, or hypoadrenalism was 3.6% (95% C.I., 0 - 8.6%), 3.3% (95% C.I., 0 - 7.7%), and 4.9% (95% C.I., 0 - 10.4%), respectively.

Conclusion: In a highly selected group of acromegalic patients, SR treatment had good efficacy and safety. This may lead to reconsider the role of SR in the therapeutic algorithm of acromegaly.