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(n) (the nadir GH during OST), Delta GH1 (= [GH(0h)-GH(n)]/GH(0h), GH(0h) was the baseline GH during OST), Delta GH2 (= [GH(m)-GH(n)]/GH(m), GH(m) was the mean GH on day curve), AUC((0-6h)) (the GH area under the curve during OST), Delta AUC1 (= [GH(0h)-AUC((0-6h))]/GH(0h)), Delta AUC2 (=[GH(m)-AUC((0-6h))]/GH(m)), AUC((m-6h)) (the GH AUC during OST where GH(m) was used instead of GH(0h)), Delta AUC1' (=[GH(0h)-AUC((m-6h))]/GH(0h)) and Delta AUC2' (=[GH(m)-AUC((m-6h))]/GH(m)). The Youden indices were calculated to determine the optimal cutoffs to predict the short-term efficacy of SSA. Delta GH2 more than 86.83%, Delta AUC2 more than -57.48% and Delta AUC2' more than -57.98% provided the best predictors of a good GH response (sensitivity 93.8%, specificity 85.7%). Delta GH2 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(n) (Delta GH) was a better predictive parameter than GH(n). 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(m) is better to be used as basal GH than GH(0) during OST.