Efficacy of cabergoline add-on therapy in patients with acromegaly resistance to somatostatin analogs treatment and the review of literature

OBJECTIVE: It is reported that adding cabergoline to somatostatin analog (SSA) normalizes IGF-1 levels approximately in one-third of patients with acromegaly. We investigated the effect of combination therapy and potential predictors of response in patients with acromegaly who do not respond to SSA therapy alone. SUBJECTS AND METHODS: Fifty acromegaly patients (M/F 23/27, mean age 50.88 ± 12.34 years) were divided into two groups as the active and control groups in this connection. Before and after treatment, we not only evaluated serum GH and IGF-1 levels and tumor size but also analyzed the factors relevant to the effect of the combined therapy. RESULTS: Adding cabergoline to SSA treatment led to IGF-1 normalization in 42% (21/50) of patients. Mean GH levels decreased from 2.64 ± 1.79 to 1.34 ± 0.99 ng/mL (p < .0001) and IGF-1 levels decreased from 432.92 ± 155.61 to 292.52 ± 126.15 ng/mL (p < .0001). GH and IGF-1 reduction in percent (%) were significantly higher in the controlled group (63% to 40%, p = 0.023 and 45% to 19%, p = 0.0001). Moreover, tumor size decrease was significantly higher in controlled group (-3.6 cm to -1.66 cm, p = 0.005). CONCLUSIONS: According to the results of our study, the addition of cabergoline to SSA normalized IGF-1 levels in a considerable amount of acromegaly patients with a moderately elevated IGF-1 level, regardless of serum PRL levels. Besides, cabergoline treatment was also influential in patients with higher IGF-1 levels despite a lower remission rate.