SUN-100 - A Case of Dopamine-Resistant and Aggressive Prolactinoma

Introduction: Prolactinomas are categorized by size, pathology, and clinical features. Dopamine agonists, cabergoline and bromocriptine, are the primary agents used for medical therapy. In instances of inadequate response or compression of adjacent structures, transsphenoidal surgery is warranted. Dopamine-resistant prolactinomas represent a rare condition, diagnosed by the failure to normalize prolactin levels and achieve a reduction in tumor size by 50% or more. We present a case report of a patient with a dopamine-resistant macroprolactinoma exhibiting aggressive behavior, who, following surgery and adjuvant chemoradiation, successfully delivered twins through assisted reproductive technology.

Case Description: A 22-year-old woman with history of type 2 diabetes presented with a 2-year history of amenorrhea. Diagnostic evaluation revealed prolactin was elevated at 81.9 µg/L (4.79-23.30 µg/L), with a low TSH level of 0.25 mIU/L (0.32-4.00 mIU/L) and low estradiol at 43 pmol/L, while LH and FSH were within normal limits at 3.1 IU/L and 6.2 IU/L, respectively. These findings were consistent with central hypothyroidism and central hypogonadism, prompting further investigation with MRI sella, which revealed a 3.1 cm x 2.5 cm x 1.8 cm mass within the sella, exerting a mass effect on the optic chiasm. She underwent surgical resection to alleviate pressure on the optic chiasm. Histopathology showed positive immunohistochemical staining for prolactin, rare cells staining for GH, a Ki-67 index of approximately 3%, and positivity for p53. Due to incomplete resection and persistently elevated prolactin, cabergoline therapy was initiated. Despite high-dose treatment (2 mg twice weekly), prolactin remained elevated, and there was an interval size increase of the sellar mass, with displacement of the optic chiasm. Subsequently, she received concurrent treatment with cabergoline and a chemotherapeutic agent, temozolomide, completing six cycles, which did not alter the size of the lesion. She then underwent radiation therapy (50 Gy, 30 fractions). Despite these interventions, the lesion increased in size; however, her prolactin began to normalize approximately eight months post-radiation therapy. Notably, despite a normal prolactin of 23.9 µg/L, her LH was low at < 0.1 IU/L, FSH at 1.7 IU/L, estradiol at 65 pmol/L, and progesterone at < 0.6 nmol/L. Despite these hormonal imbalances, she became pregnant and continued cabergoline during pregnancy. She delivered twin girls at 35 weeks and 4 days via caesarean section due to decreased growth velocity and abnormal doppler findings. Both twins are currently in good health.

Conclusion: Dopamine-resistant prolactinomas are uncommon, challenging to treat, often associated with poor prognosis. Nonetheless, through the implementation of multimodal therapy and a fertility-focused approach, successful pregnancy outcomes can be achieved.

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