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Single-session stereotactic radiotherapy can be a safe and effective treatment for acromegalic patients with residual or recurrent growth-hormone secreting adenoma, researchers report.

Single-session stereotactic radiotherapy (SR) can be a safe and effective treatment for acromegalic patients with residual or recurrent growth-hormone secreting adenoma, Italian researchers report.

The treatment of choice for most patients with acromegaly is transsphenoidal surgery to remove the pituitary tumor, yet approximately 40 per cent of patients will not achieve remission, the report indicates. Those patients not cured by surgery or who experience a recurrence are candidates for treatment with medications or radiotherapy.

Prior research has shown that precise and potent radiation produced with SR can reduce growth hormone levels more rapidly than can fractionated radiotherapy, note lead author Dr. Marco Losa and colleagues from Universita Vita-Salute in Milan. Still, data are lacking about the long-term efficacy of SR in acromegalic patients.

The current investigation involved 83 patients who had a residual or recurrent active adenoma after having undergone maximal surgical debulking at the researchers' center. The goal of SR was to achieve normal levels of insulin-like growth factor 1 while keeping basal growth hormone levels below 2.5 micrograms/L without resorting to growth hormone-suppressing drugs. The median follow-up period was 69 months.

Overall, 50 patients (60.2 per cent) achieved the therapeutic goal, the researchers report. The five-year remission rate was 52.6 per cent, according to the report in the Journal of Clinical Endocrinology and Metabolism for July.

In an additional 13 patients (15.7 per cent) who had been resistant to somatostatin analogs, SR, along with continued analog therapy, achieved disease remission.
On multivariate analysis, low basal levels of growth hormone and insulin-like growth factor were predictive of treatment success.

No serious adverse effects were seen with SR and the five-year cumulative risks of new onset hypogonadism, hypothyroidism, or hypoadrenalism did not exceed 4.9 per cent.

"SR treatment might be considered as an alternative to lifelong treatment with somatostatin analogs or growth hormone receptor antagonists, particularly in patients with small tumor residue located away from the optic pathway and the residual normal pituitary gland," the research team concludes.

J Clin Endocrinol Metab 2008;93:2546-2552