Background: Whether the withdrawal of treatment in patients with nontumoral hyperprolactinemia, microprolactinomas, or macroprolactinomas is safe and effective has been unclear. We performed an observational, prospective study of cabergoline (a dopamine-receptor agonist) withdrawal in such patients.

Methods: The study population included 200 patients--25 patients with nontumoral hyperprolactinemia, 105 with microprolactinomas, and 70 with macroprolactinomas. Withdrawal of cabergoline was considered if prolactin levels were normal, magnetic resonance imaging (MRI) showed no tumor (or tumor reduction of 50 percent or more, with the tumor at a distance of more than 5 mm from the optic chiasm, and no invasion of the cavernous sinuses or other critical areas), and if follow-up after withdrawal could be continued for at least 24 months.

Results: Recurrence rates two to five years after the withdrawal of cabergoline were 24 percent in patients with nontumoral hyperprolactinemia, 31 percent in patients with microprolactinomas, and 36 percent in patients; with macroprolactinomas. Renewed tumor growth did not occur in any patient; in 10 female patients (22 percent) and 7 male patients (39 percent) with recurrent hyperprolactinemia, gonadal dysfunction redeveloped. In all diagnostic groups, prolactin levels at the time of recurrence were significantly lower than at diagnosis (P<0.001). The Kaplan-Meier estimated rate of recurrence at five years was higher among patients with macroprolactinomas and those with microprolactinomas who had small remnant tumors visible on MRI at the time of treatment withdrawal than among patients whose MRI scans showed no evidence of tumor at the time of withdrawal (patients with macroprolactinomas, 78 percent vs. 33 percent, P=0.001; patients with microprolactinomas, 42 percent vs. 26 percent, P=0.02).

Conclusions: Cabergoline can be safely withdrawn in patients with normalized prolactin levels and no evidence of tumor. However, because the length of follow-up in our study was insufficient to rule out a delayed increase in the size of the tumor, we suggest that patients be closely monitored, particularly those with macroprolactinomas, in whom renewed growth of the tumor may compromise vision.