Long-term response to cabergoline and multi-modal treatment in men with macroprolactinoma: Does size really matter?

Objective: To study the outcome of men with macroprolactinoma following cabergoline treatment based on tumour size. Design: Retrospective cohort study. Methods: The study included 94 men, divided into three groups according to adenoma diameter: 10–19 mm (Group A, n = 36); 20–39 mm (Group B, n = 41); or ≥40 mm (Group C, giant prolactinomas, n = 17). Patients were followed for a mean of 7.5 years with sellar magnetic resonance imaging, visual fields and hormone measurements. Results: Mean baseline prolactin was 767, 2090 and 24,806 ng/ml in Groups A, B and C, respectively (p <.01). Prolactin suppression below three times the upper limit of normal (ULN) was achieved in 34 (94%; mean weekly cabergoline dose of 1.2 mg), 37 (90%; cabergoline dose, 2.1 mg) and 15 (88%; cabergoline dose, 2.8 mg) men (p =.31) in each group. After excluding patients who underwent surgery and radiotherapy, cabergoline suppressed prolactin below three times ULN in 32/35 (91%), 29/37 (78%) and 11/14 (79%) men in Groups A, B and C, respectively (p =.27). Visual deficits were observed in 5 (14%), 12 (29%) and 10 (59%) patients (p <.01); improvement was achieved in 5/5 (100%), 11/12 (92%) and 10/10 (100%) of men in Groups A, B and C. Low baseline testosterone was measured in 26 (72%), 39 (95%) and 17 (100%) patients in the three groups (p <.01). Following multi-modal treatment, hypogonadism persisted in 3 (8%), 5 (12%) and 2 (12%) men, respectively (p =.85). Conclusion: Macroprolactinomas in men were controlled with cabergoline in 84% of cases, independent of tumour size. Pituitary surgery and adjuvant radiotherapy further improved long-term response to 91%.