From wikipedia:
"adjunctive therapy of acromegaly, cabergoline has low efficacy in suppressing growth hormone levels and is highly efficient in suppressing hyperprolactinemia that is present in 20-30% of acromegaly cases; growth hormone and prolactin are similar structurally and have similar effects in many target tissues, therefore targeting prolactin may help symptoms when growth hormone secretion can not be sufficiently controlled by other methods"
Also, I'm not sure wheter using dopamine agonists without real prolactin issues is good idea.