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

To study the outcome of men with macroprolactinoma following cabergoline treatment based on tumour size.

Retrospective cohort study.

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.

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).

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%.