Can cabergoline (dopamine agonist) reduce the size of a large prolactinoma (prolactin-secreting pituitary tumor)?

From the Guidelines

Yes, cabergoline can effectively shrink very large prolactinomas, with significant tumor shrinkage and improvement in symptoms, as supported by recent evidence 1.

Key Points

• Cabergoline is a dopamine agonist medication that is the first-line treatment for prolactinomas of all sizes, including macroadenomas (>10mm) and giant prolactinomas (>4cm) 1.
• The typical starting dose is 0.25mg twice weekly, gradually increasing as needed to 0.5-1mg twice weekly, with some patients requiring higher doses up to 4mg weekly for very large tumors.
• Most patients experience significant tumor shrinkage within 3-6 months of starting treatment, with reductions in tumor volume ranging from 50-90% 1.
• Along with tumor shrinkage, cabergoline normalizes prolactin levels and resolves symptoms like visual field defects, headaches, and hormonal disturbances 1.
• Treatment is typically long-term, often continuing for 2-5 years or longer, with regular monitoring of prolactin levels, tumor size via MRI, and potential side effects like nausea, dizziness, and fatigue.
• Cabergoline is preferred over surgery for most prolactinomas because of its high efficacy and lower risk profile 1.

Important Considerations

• Medication-induced shrinkage of prolactinomas that have invaded sphenoid bone can cause rhinorrhoea after a few months of drug administration due to a cerebrospinal fluid leak 1.
• Detection of β2-transferrin or β-trace protein in nasal secretions confirms a cerebrospinal fluid leak, which may require urgent intervention 1.
• Apoplexy has been described during cabergoline therapy both in adults and children with prolactinomas 1.

From the Research

Efficacy of Cabergoline in Shrinking Large Prolactinomas

• Cabergoline has been shown to be effective in shrinking large prolactinomas, with a significant reduction in tumor size observed in several studies 2, 3, 4, 5, 6.
• In a study of 10 men with giant prolactinomas, cabergoline treatment resulted in a significant decrease in prolactin levels and tumor shrinkage in 9 out of 10 patients, with a volume reduction of greater than 95% in 3 patients 2.
• Another study found that cabergoline was effective in normalizing prolactin levels and inducing tumor shrinkage in patients with macroprolactinomas, with a significant reduction in tumor size observed in the majority of patients 3.
• The efficacy of cabergoline in shrinking large prolactinomas is thought to be due to its ability to bind to dopamine receptors, which inhibits the production of prolactin and leads to a decrease in tumor size 4, 5, 6.

Comparison with Other Treatments

• Cabergoline has been compared to other dopamine agonists, such as bromocriptine, and has been found to be more effective and better tolerated in many cases 3, 5.
• A study comparing cabergoline and bromocriptine found that cabergoline was more effective in reducing prolactin levels and inducing tumor shrinkage, with fewer adverse events reported 5.
• The long-term efficacy and safety of cabergoline have also been demonstrated in several studies, with stable normalization of prolactin levels achieved in the majority of patients and few adverse events reported 6.

Tumor Shrinkage and Clinical Outcomes

• The shrinkage of large prolactinomas with cabergoline treatment has been associated with improved clinical outcomes, including the resolution of visual field defects and the restoration of normal menstrual function in women 2, 3, 6.
• In a study of 162 women with hyperprolactinemic disorders, cabergoline treatment resulted in the resumption of regular menses in 91% of previously amenorrhoeic women and 90% of previously oligomenorrhoeic women 6.
• The improvement in clinical outcomes with cabergoline treatment is thought to be due to the reduction in prolactin levels and tumor size, which leads to a decrease in the mass effect of the tumor and an improvement in pituitary function 2, 3, 6.