Pasireotide: A potential therapeutic alternative for resistant prolactinoma

Area of Science:

• Endocrinology
• Oncology

Background:

• Approximately 10% of prolactinomas are resistant to dopamine agonists (DAs).
• Current alternatives for DA-resistant prolactinomas include surgery or radiotherapy.
• First-generation somatostatin analogs have shown no efficacy, and the efficacy of pasireotide is unexplored.

Observation:

• A 41-year-old woman with a macroprolactinoma resistant to all DAs was treated with pasireotide long-acting release (LAR).
• The patient had a history of two debulking surgeries.
• Tumor pathology revealed high somatostatin receptor subtype 5 (SSTR5) and low SSTR2 expression.

Findings:

• Pasireotide LAR monotherapy normalized prolactin levels and resolved symptoms within one month.
• Clinical benefits, including normal prolactin levels and stable tumor volume, were sustained for seven years.
• Glucose tolerance remained satisfactory during treatment.

Implications:

• Pasireotide is a potential alternative treatment for dopamine-agonist-resistant prolactinomas.
• Long-term control of prolactin levels and tumor volume is achievable with pasireotide monotherapy.
• Somatostatin receptor expression analysis may guide patient selection for pasireotide treatment.