SUN-272 Significant Response to Temozolomide in Two Aggressively Growing Pituitary Adenomas

Introduction: Aggressive atypical pituitary tumors are characterized by invasive growth, recurrence and resistance to standard therapies. We present two female patients with pituitary adenomas in whom multiple other therapies had failed, who presented with significant response to temozolomide. Case presentations: In patient #1 (w, 78y), the diagnosis of macroprolactinoma had been made in a community hospital and dopaminagonistic treatment with bromocriptin had been initiated. After failure to achieve significant tumor reduction under this treatment and persisting visual field disturbances, first transnasal-transphenoidal surgery (TSS) was performed in 07/2011, followed by cabergoline exposure in increasing dose due to failure to control prolactin levels. Repeat TSS and stereotactic radiosurgery were performed in both 2014 and 2018 because of invasive tumor growth and double vision. She was then put on temozolomide. Patient #2 (w, 58y) presented with apoplectic gonadotropinoma in 2013. She also underwent 3 courses of TSS as well as stereotactic radiosurgery because of repeated tumor growth leading to visual field disturbances and double vision. Despite these measures, the tumor could not be controlled and she, as well, was put on temozolomide in 2018. In both cases costs were reimbursed by the patient’s health care insurance and in both the first cycle was conducted with 150 mg/ body surface area (BSA) with escalation to 200 mg/BSA in the second. After only 2 cycles, double vision resolved in both patients and the tumor had shrunk by approximately 20% on MRI in patient #1 and even more in patient #2. In both patients, temozolomide dose was reduced again to 150 mg/BSA due to side effects. Nevertheless, in both patients tumor volume further continued to decrease under therapy. Conclusion: This promising clinical course after exposure to temozolomide with early, significant tumor shrinkage in two heavily pretreated patients with aggressive pituitary adenomas indicates that this therapy can be considered also in older patients and may yield astonishing results. Although temozolomide is increasingly becoming a therapeutic option for those patients whose pituitary tumors are refractory to standard therapies, further research and observance over time of temozolomide therapy in aggressive pituitary adenomas and carcinomas is indicated.