INNV-38. Long-term survival in a patient with metastatic prolactinoma: A 12-year follow-up

Abstract Metastatic prolactinomas are an extremely rare type of neuroendocrine tumors, comprising less than 0.2% of all pituitary tumors. These tumors are typically associated with poor prognosis, with an average survival of 10 months. Temozolomide (TMZ) has previously been shown to be effective in treating these rare cases once first-line medical, surgical and radiation therapies have failed. We present the case of a 56-year-old male who first presented in 2012 with peripheral vision changes. Workup revealed prolactin levels >1000 ng/mL and a brain MRI showed a pituitary macroadenoma. He was treated with dopamine agonists, surgical management as well as radiation. In 2018, MRI revealed a new mass along the posterior left basiocciput encroaching the hypoglossal canal and a prolactin level of 102 ng/mL. The patient underwent proton therapy and increased cabergoline dosing. In 2020, the patient presented with left leg weakness, and numbness. MRI of the thoracic and lumbar spine revealed multiple enhancing intradural extramedullary masses within the spinal canal. He underwent a resection of the largest mass and pathology confirmed metastatic prolactinoma. The patient began monthly TMZ chemotherapy. Prolactin levels dropped from 247.3 ng/mL to 1.5 mg/mL after six cycles, coinciding with tumor reduction and improvements in lower extremity strength. In 2021, a chemotherapy holiday was initiated, however, by mid-2023, prolactin levels rose to 63.1 ng/mL, and an MRI of the lumbar spine showed an increase in lumbar metastasis size. The patient began a TMZ rechallenge. After two cycles, prolactin levels dropped to 5.7 ng/mL with stable imaging. As of early 2025, imaging has shown no new metastatic lesions and stabilization of the lumbar lesion, and lab work has demonstrated stable prolactin levels. Despite an initially poor prognosis, the patient has survived for over a decade since the diagnosis of prolactinoma and more than four years since the metastatic spread.