Early prediction of long-term response to cabergoline in patients with macroprolactinomas

Abstract

Cabergoline is effective for treating prolactinomas. However, some patients display cabergoline resistance, and their early characteristics are not well known. We analyzed early indicators predicting the long-term response to cabergoline. We retrospectively reviewed 44 patients with macroprolactinomas who received cabergoline as first-line treatment; the patients were followed-up for a median of 16 months. The influences of various clinical parameters on outcomes were evaluated. Forty patients (90.9%) could be medically treated, displaying tumor volume reduction (TVR) of 74.7%, prolactin normalization (NP) rate of 81.8%, and complete response (CR; TVR>50% with NP, without surgery) rate of 70.5%. Most patients (93.1%) with TVR≥25% and NP at 3 months eventually achieved CR, whereas 50% of patients with TVR≥25% without NP and no patient without TVR≥25% achieved CR. TVR at 3 months was strongly correlated with the final TVR (R=0.785). Patients with large macroadenomas exhibited a low NP rate at 3 months but eventually achieved TVR and NP rates similar to those of patients with smaller tumors. Surgery independently reduced the final dose of cabergoline (β=−1.181 mg/week), and two of four patients who underwent surgery could discontinue cabergoline. Determining cabergoline response using TVR and NP at 3 months after treatment is useful for predicting later outcomes. However, further cabergoline administration should be considered for patients with TVR>25% at 3 months without NP, especially with huge prolactinomas, because a delayed response may be achieved. As surgery can reduce the cabergoline dose with successful disease control, it should be considered for cabergoline-resistant patients.