SAT-247 Use of Double Dopamine Agonists in Giant Prolactinomas: A Series of 6 Cases

Dopamine agonist monotherapy is first line therapy in giant prolactinomas even when visual field defect is present. The costlier cabergoline is often preferred over bromocriptine due to higher efficacy and tolerability profile. Described herein combined cabergoline and bromocriptine therapy in 6 cases of giant prolactinomas. Retrospective records review of 6 patients with giant prolactinoma (3 males: M1-M3, 3 females: F1-F3) in a single tertiary centre was performed. Mean age at diagnosis: 29 years (range 17-39). Mean duration of follow up: 7 years (range 3-11). Headache and visual field defect were the presenting symptoms in all cases. Basal prolactin concentration: 100000 to 468851 mIU/L (<300 for male, <600 for female). Three patients have hypopituitarism at presentation, one after surgery and one remained eupitary 5 years after diagnosis. One developed late onset hypopituitarism 4 years after normalisation of prolactin levels. Three patients underwent debulking at presentation because of significant mass effects with obstructive hydrocephalus. In all patients cabergoline 1-1.5 mg/wk was started at diagnosis and gradually increased to 0.5 mg daily, aiming for normoprolactinemia. From May 2017 bromocriptine were given to these patients who continued to have hyperprolactinemia despite cabergoline 3.5-4mg/wk. Bromocriptine was commenced 1.25-5mg/day and gradually increased to 10 mg/day on top of cabergoline with careful monitoring of prolactin levels and side effects. Cabergoline was tapered down to 1.5-2mg/wk if prolactin levels remained stable between 2-3x normal while maintaining dose of bromocriptine. In M1, cabergoline was tapered off while maintaining bromocriptine 10mg/day with stable prolactin levels (~1000 mIU/L). In M2, normoprolactinemia was achieved after adding on bromocriptine and is currently on cabergoline 2mg/week and bromocriptine 10mg/day. In M3, whose prolactin were 4x normal value despite cabergoline 3.5mg/week, decreased 50% with bromocriptine 5 mg/day and remained stable when cabergoline reduced to 1.5mg/week. F1 had transphenoidal section twice due to failure of medical therapy. Her prolactin remained markedly elevated 10000-20000 mIU/L despite cabergoline 3.5 mg/week and bromocriptine 10mg/day, with persistent bitemporal hemianopia. F2 developed erythema nodosum after starting bromocriptine which was stopped and continued with cabergoline 1 mg/week. F3 showed partial response with 50% reduction in prolactin to 4485 mIU/L with bromocriptine 10 mg/day and cabergoline 1.5mg/week. In patients who underwent debulking, residual tumour remained unchanged. Two patients - tumour shrank 40% (F2) and 90% (M3) with medical therapy alone. In conclusion, adding on bromocriptine can be considered when high dose cabergoline is required for treatment of giant prolactinoma with careful monitoring. This reduces cabergoline dose which saves cost.