The value of an acute octreotide suppression test in predicting short-term efficacy of somatostatin analogues in acromegaly.

Predicting the efficacy of long-acting somatostatin analogues (SSA) remains a challenge. We aim to quantitatively evaluate the predictive value of the octreotide suppression test (OST) in short-term efficacy of SSA in active acromegaly. Sixty-seven newly diagnosed acromegaly patients were assessed with OST. Subsequently, all patients were treated with long-acting SSA for 3 months, followed by reassessment. Nine parameters were tested, including GH (the nadir GH during OST), ΔGH1 (= [GH-GH]/GH, GH was the baseline GH during OST), ΔGH2 (= [GH-GH]/GH, GH was the mean GH on day curve), AUC (the GH area under the curve during OST) , ΔAUC1 (= [GH-AUC]/GH), ΔAUC2 (=[GH-AUC]/GH), AUC (the GH AUC during OST where GH was used instead of GH), ΔAUC1' (=[GH-AUC]/GH) and ΔAUC2' (=[GH-AUC]/GH). The Youden indices were calculated to determine the optimal cutoffs to predict the short-term efficacy of SSA. ΔGH2 more than 86.83%, ΔAUC2 more than -57.48% and ΔAUC2' more than -57.98% provided the best predictors of a good GH response (sensitivity 93.8%, specificity 85.7%). ΔGH2 more than 90.51% provided the best predictor of a good tumor size response (sensitivity 84.8%, specificity 87.5%). The percentage fall of GH (ΔGH) was a better predictive parameter than GH. OST showed higher efficiency in predicting the efficacy of octreotide LAR than lanreotide SR. In conclusion, OST is a valid tool to predict both GH and tumor size response to short-term efficacy of SSA in acromegaly, especially for octreotide LAR. GH is better to be used as basal GH than GH during OST.