Long-term primary pharmacotherapy of giant prolactinomas: A comparison of different cabergoline dosages

Dopamine agonists serve as first-line therapies for most giant prolactinomas. The objective of this study was to assess the differential impact of dopamine agonist dosing strategies on biochemical (prolactin normalisation) and radiological (tumour size reduction) responses in patients with giant prolactinomas.

A single-centre retrospective real-life 23-year follow-up study.

Thirty-three patients with giant prolactinomas (≥ 4 cm) were treated with primary pharmacotherapy. We assessed pituitary function, the effect of therapy and different dosing regimens on prolactin normalisation and tumour size, the effect of surgery for complications and the effect of radiotherapy in resistant patients.

Out of thirty-three consecutive patients (mean age 42 years), 27 were men, and 6 were women. The baseline mean prolactin concentration was 7506 µg/L. The treatment of choice was cabergoline in 30 patients, terguride in 2 patients, and bromocriptine in 1 patient. In patients receiving a high dose of cabergoline (3.5 mg weekly), we observed a faster normalisation of prolactin but not faster reduction in tumour size than in patients receiving a low dose (1-2.5 mg weekly). A total of 9/33 (27 %) patients underwent surgery for complications, 3 of whom were irradiated by Leksell gamma knife for partial resistance. In 4/33 patients we were able to stop pharmacotherapy after 10-20 years of treatment. The remaining 29/33 patients remained on pharmacological treatment.

Dopamine agonists are safe and only required treatment in 2/3 of patients treated with pharmacotherapy as a first-line treatment. Higher doses of cabergoline accelerate prolactin normalisation but do not confer additional benefit in early tumour shrinkage.