Effectiveness of Cabergoline in Reduction of Tumor Volume and Suppression of Prolactin in Treatment-Naive Prolactinomas and the Correlation of T2-weighted Signal Characteristics of Adenomas with Their Response to Treatment

Abstract

Objective: Cabergoline is a potent dopamine receptor agonist commonly used in the treatment of hyperprolactinemia. However, there are scarce data on the imaging characteristics of prolactinomas that could predict the response to treatment. The present study prospectively evaluated the effectiveness of cabergoline in the reduction of tumor volume and serum prolactin levels in treatmentnaive cases of prolactinomas besides evaluating the imaging features of tumors on T2-weighted magnetic resonance imaging that could potentially predict the response to treatment. Methods: The present study evaluated 83 prolactinomas (52 micro- and 31 macroprolactinomas) for a 24-month period. The T2-weighted signal characteristics of prolactinomas were evaluated at the start of treatment in addition to the estimation of tumor volumes and prolactin levels. T2-weighted signal characteristics of tumors allowed the categorization of tumors into homogeneous and heterogeneous groups. Patients were started on cabergoline therapy, and thereafter, serial magnetic resonance imagings were performed at 4-, 8-, 12-, 18-, and 24-month intervals to monitor the changes in tumor volume and prolactin levels. Results: A total of 30 (27 micro- and 3 macroadenomas) patients showed complete disappearance of tumor at 24 months. More than a 75% reduction in tumor volume was noted in 82.7% of microadenomas and 78.6% of macroadenomas. More than a 75% reduction in prolactin levels was seen in 88.5% of microadenomas and 77.9% of macroadenomas at 24 months. After 1 year of treatment with cabergoline, 68.6% (35/51) showed normalization of prolactin levels and 64.7% (33/51) showed more than 50% reduction in tumor volume in the homogeneous group. In comparison, only 28.12% (9/32) showed normalization of prolactin levels and 31.25% (11/32) showed >50% tumor volume reduction among the heterogeneous group. Heterogeneous prolactinomas had more number of macroadenomas and were significantly larger and more secreting compared to homogeneous tumors at baseline (all P < .05) Conclusion: Cabergoline administered for 12-24 months induced a significant tumor volume reduction with amelioration of clinical symptoms of prolactin excess and normalization of serum prolactin levels. T2-weighted homogeneous tumors had a more favorable outcome in comparison to the heterogeneous tumors.