Does medical treatment shrink prolactinomas?

From the Guidelines

Medical treatment with dopamine agonists, specifically cabergoline, is highly effective in shrinking prolactinomas, with tumor shrinkage achieved in approximately 62% of patients. Dopamine agonists reduce pituitary-origin hyperprolactinaemia of any cause, and in adults with prolactinoma, they induce normalization of the prolactin level, tumour shrinkage, resolution of visual field defects, normalization of menses, fertility, and sexual function, and resolution of galactorrhoea 1.

Key Points

• Cabergoline is the dopamine agonist of choice for treating prolactinoma in both adults and children, due to its longer half-life and greater affinity for the dopamine receptor than other dopamine agonists 1.
• Treatment with cabergoline typically results in normalization of prolactin levels in 68% of patients, tumour shrinkage in 62%, and resolution of visual field defects in 67% 1.
• Regular monitoring of prolactin levels and periodic MRI scans are necessary to assess treatment response and adjust the dose as needed.
• Side effects may include nausea, dizziness, and headache, which often improve with continued use or dose adjustments.

Treatment Approach

• Dopamine agonists like cabergoline (typically 0.25-1 mg twice weekly) are the first-line treatments for prolactinoma.
• Treatment typically continues for at least 2 years, after which some patients with sustained normal prolactin levels and significant tumor shrinkage may attempt medication withdrawal under medical supervision.
• For the small percentage of patients who don't respond to medication, surgery may be considered as an alternative approach. In a randomized controlled trial of adult women with prolactinoma, cabergoline was superior to bromocriptine in normalizing prolactin (83% versus 59%), resuming ovulatory cycles or achieving pregnancy, with fewer adverse events reported with cabergoline than with bromocriptine (52% versus 72%) 1.

From the FDA Drug Label

Reduction in tumor size has been demonstrated in both male and female patients with macroadenomas In cases where adenectomy is elected, a course of bromocriptine mesylate tablets, USP therapy may be used to reduce the tumor mass prior to surgery. Effective treatment with bromocriptine mesylate leads to a reduction in hyperprolactinemia and often to a resolution of the visual impairment Discontinuation of bromocriptine mesylate treatment in patients with known macroadenomas has been associated with rapid regrowth of tumor and increase in serum prolactin in most cases

Medical treatment with bromocriptine can shrink prolactinomas, as evidenced by the reduction in tumor size in patients with macroadenomas and the improvement in visual field impairment. However, discontinuation of treatment can lead to rapid regrowth of the tumor 2 2.

• Key benefits of bromocriptine treatment include:
  • Reduction in tumor size
  • Improvement in visual field impairment
  • Reduction in hyperprolactinemia
• Important considerations:
  • Discontinuation of treatment can lead to rapid regrowth of the tumor
  • Patients should be carefully monitored for signs of tumor expansion during treatment

From the Research

Medical Treatment of Prolactinomas

• Medical treatment with dopamine agonists (DAs) is the primary treatment for prolactinomas, with cabergoline being the main agent used 3, 4, 5, 6.
• Cabergoline has been shown to normalize prolactin levels in up to 85% of patients and cause tumor shrinkage in up to 80% of patients 3.
• The efficacy of cabergoline in achieving normoprolactinemia and tumor shrinkage varies depending on the type of prolactinoma, with microprolactinomas responding better than macroprolactinomas 4.

Tumor Shrinkage

• Tumor shrinkage is a common outcome of medical treatment with DAs, with up to 80% of patients experiencing significant reduction in tumor size 3.
• The degree of tumor shrinkage can vary depending on the individual patient and the specific type of prolactinoma 5.
• In some cases, tumor shrinkage can be significant enough to alleviate mass effects and improve symptoms 6.

Resistance to Medical Treatment

• Some patients may be resistant to medical treatment with DAs, requiring alternative treatment options such as surgery, radiation therapy, or multimodality therapy 3, 5, 7.
• Patients with aggressive or malignant prolactinomas may require more intensive treatment, including high-dose cabergoline, surgery, and radiation therapy 3, 5.
• Experimental treatments, such as temozolomide, aromatase inhibitors, and immune-checkpoint inhibitors, may be effective in some patients with refractory prolactinomas, but more research is needed to fully understand their efficacy and safety 5.