Endocrine Abstracts

69-year old male was diagnosed with non-secreting pituitary macroadenoma (25x 15x 15mm) in 2008. Patient underwent two transsphenoidal surgeries and stereotactic radiotherapy in 2008 and 2009. Tumor recurrence was noticed on MRI in 2016. In 2017 urgent right pterional craniotomy was performer due to right eyelid dropping with ocular nerves palsy. Despite surgery further growth of the tumor (32x 22x 31mm) was reported in 2018, followed by increased ACTH level and hypercortisolemia in 2019. It was decided to start therapy with pasireotide. Patient received 5 doses of pasireotide LAR between September 2019 and June 2020. In September 2019 cortisol level was 21µg/dl (3.7-19.4), and ACTH 107 pg/ml (0-46) before administration and increased up to 35.6µg/dl, and 176 pg/ml after it. This was the first time when paradoxical response was noticed. 2nd and 3rd doses were administered in October and in November 2019 without increase of cortisol or ACTH concentration and MRI showed marked regression of tumor one month later. 4th dose was administered in March and 5th dose in June 2020. There was no paradoxical response. Recurrence of hypercortisolemia and tumor progression were observed in February 2021. Cortisol level was 53.3µg/dl and ACTH 246 pg/ml. In March 2021 6th dose of pasireotide was administered. Then 2nd paradoxical response occured. Cortisol level increased up to 83.5µg/dl, and ACTH up to 392 pg/ml After metyrapone treatment cortisol concentration decreased and hydrocortisone was necessary. In April 2021 patient received 7th dose of pasireotide. Cortisol level was 10.2µg/dl and ACTH 149 pg/ml. After one week laboratory results confirmed 3rd paradoxical response to pasireotide (cortisol 59.3µg/dl and ACTH 186 pg/ml). In February 2022 cortisol level was very low (up to 4.6µg/dl) and ACTH decreased to 47.2 pg/ml. >MRI revealed marked regression of tumor mass. Pasireotide wasn’t administered. In August 2022 it turned out that cortisol and ACTH concentration were increased (60.3µg/dl and 242 pg/ml). Severe hypercortisolemia was observed few weeks later despite metyrapone treatment. It was decided to administer pasireotide once again. In October 2022 patient received 8th dose and 4th paradoxical response occured. The rebounds in increase of cortisol were severe and required steroidogenesis inhibitors for few months. During this period the highest level of cortisol was 91µg/dl and ACTH 816 pg/ml. Treatment with pasireotide was considered as the emergency therapy. Pasireotide affects both tumor size and cortisol production and effects are likely to appear much earlier than after radiotherapy. Poor patient conditions and irregular growth of the tumor suggested against surgery.