The predictors of the response to somatostatin analogue therapy in patients with acromegaly
Dong-Sun Kim1, Joo-Hyung Kim2, Sin-Gon Kim Kim2, Sei-Hyun Baik2, Soon-Jib Yoo3 & Yeon-Ah Sung4
Somatostatin analogues (SSA) are widely used for the treatment of patients with acromegaly, and the responses are variable. We investigated the possible predictive factors of the response to SSA therapy in Korean acromegalic patients. Twenty-eight patients were retrospectively analysed, who were treated by surgery and adjunctively SSA. Somatostatin suppression tests (SST, hourly GH measurements for 3 h following 100 μg somatostatin injection) were done before SSAs were given. The good response to SSA treatment was defined as a normal IGF1 for age and a GH <2.5 ng/ml. After SSA therapy, decrease of GH below 2.5 ng/ml and normalization of IGF1 were achieved in 40 and 46.4% of the patients, respectively. It was 26.7% who showed both of normal IGF1 and GH <2.5 ng/ml. There were no significant differences in gender, age, tumor size, postoperative residual tumor, baseline GH/IGF1 and decrement of postoperative GH levels between the good and poor responders. However, nadir GH (0.94 vs 3.11, P<0.05), mean GH (1.37 vs 4.36, P<0.05), and GH fall (90.6 vs 83.5%, P<0.01) in SST were significantly different between two groups. In addition, there were significant correlations between nadir and mean levels of GH during SST and post-treatment levels of IGF1. In ROC curve analysis, the highest cut-off value in predicting achievement of normal IGF1 was 2.94 ng/ml of mean GH and 2.30 ng/ml of nadir GH during SST. Both Criterion had sensitivity 72.2%, specificity 80%, positive predictive value 86.67% and negative predictive value 61.54%. This study suggests SST has some values for prediction of the response to SSA treatment in patients with acromegaly. However, SST does not reach a value of independent predictive factor for SSA therapy, and a poor response to SST does not exclude the good response to SSA therapy.