Giant prolactinoma and effectiveness of medical management

To review our experience with long-term cabergoline and bromocriptine therapy in the treatment of giant prolactinomas.

Patients with giant prolactinomas diagnosed and treated at our center in Mumbai, India, between January 2005 and January 2009 were included. Diagnostic criteria for giant prolactinoma included tumor diameter greater than 40 mm, serum prolactin concentration higher than 1000 ng/mL, and invasive tumor growth pattern with mass effects. Cabergoline was started at a dosage of 0.5 mg weekly and progressively increased as necessary up to 3.5 mg weekly. Patients were followed up with hormone measurements, sellar magnetic resonance imaging, and vision examinations.

The study group included 10 patients (5 male and 5 female), aged 17 to 50 years (mean, 36.1 years), treated for giant prolactinoma. In 8 patients, cabergoline was first-line therapy. Two patients had previously been prescribed bromocriptine, and this regimen was maintained. Mean serum prolactin concentration before treatment was 10,789 +/- 14,278 ng/mL (range, 1256-43,163 ng/mL; reference range, 5-17 ng/mL). Following treatment, levels normalized in 7 patients within 2 to 18 months (mean, 8.8 months) and decreased in 1 patient to a level 3 to 4 times that of normal. Tumor diameter, which measured from 4 to 7 cm at diagnosis, showed a mean maximal decrease of 49.28 +/- 18.27%; response was first noted about 6 months after treatment was begun. Seven patients had visual field defects at diagnosis; vision returned to normal in 3 and improved in 4. Testosterone levels, initially low in all male patients, normalized in 3.

Cabergoline should be first-line therapy for aggressive prolactinomas, even in those patients who present with visual field defects.