Endocrine Abstracts (2008) 15 P260

Predictors of response to medical therapy in patients with acromegaly

Mark Sherlock1, Eva Fernandez-Rodriguez1, Aurora Aragon Alonso1, John Ayuk1, Richard N Clayton2, Michael C Sheppard1, Andy Bates3 & Paul M Stewart1

1Department of Medicine, Division of Medical Sciences, University of Birmingham, Birmingham, UK; 2Department of Postgraduate Medicine, University of Keele, Stoke-on-Trent, UK; 3Birmingham Heartlands and Solihull NHS Trust, Birmingham, UK.

Acromegaly is associated with increased morbidity and mortality. There are several treatment options for acromegaly including surgery, radiotherapy and medical therapy. The aims of treatment in patients with acromegaly is to achieve GH and IGF-I concentrations associated with cure or normalisation of mortality.

We examined predictive factors of response to treatment with dopamine agonists (DA) and somatostatin analogues (SSA) in a cohort of 501 patients with acromegaly (276/501, 55.1% received medical therapy at some stage during follow up). About 172/276 patients had surgery and 73/276 patients received radiotherapy prior to receiving medical therapy. About 198/276 received DA and 144/276 received SSA. For the purpose of analysis GH and IGF-I values at baseline and after 12 months on therapy were used.

In the DA group basal prolactin concentration did not predict response to therapy (GH % reduction): hyperprolactinaemia median 26.7% (IQR 10.4–48) versus normoprolactinaemia 34.8% (0.2–53.2), P=0.58. Prior surgery was associated with a less marked GH % reduction (P=0.026) and IGF-I % reduction (P=0.0043): surgery group GH 23.9% (−9.9–48.5) and IGF-I 9.2(−1.0–26.6), no surgery group GH 40.5% (15–71) and IGF-I 40 (15.4–88.2). Prior radiotherapy was associated with an enhanced GH % reduction but no significant effect on % IGF-1 reduction: no radiotherapy (GH 20.5% (−9.9–39.1), IGF-I 9.4% (−16.2–28.7)) versus radiotherapy (GH 50.8% (15.5–67.5), IGF-I 22.2% (3.1–57.9)), P=0.0029 and 0.07, respectively. In the SSA group there was no effect of prior surgery on extent of GH or IGF-I decrease, P=0.63 and 0.78, respectively. Prior radiotherapy did not have an effect on decrease in GH (P=0.77) however it did lead to a less marked IGF-1% reduction (P=0.045).

These results indicate that dopamine agonists are beneficial in patients with acromegaly irrespective of baseline prolactin concentrations. Prior surgery and radiotherapy are associated with differences in GH and IGF-I response to DA and SSA therapy.

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