SUN-443 Surgical Management of Cystic Prolactinomas

Purpose: Treatment of prolactinomas with a predominantly cystic component remains controversial. This study assessed remission rates in surgically-treated cystic prolactinomas, compared to solid micro- and macroprolactinomas. Methods: Charts were retrospectively analyzed for 57 patients who underwent transsphenoidal resection (TSS) for prolactinomas, from 2004 to 2018, by two experienced neurosurgeons. Tumors were subdivided into: cystic prolactinomas (n=17, >50% initial cystic component), microprolactinomas (n=10, <10 mm) and macroprolactinomas (n=30, ≥10 mm). Patients underwent TSS primarily for reasons of dopamine agonist (DA) intolerance, non-responders or patient preference. Remission was defined as either immediate postoperative (POD #1-3) prolactin (PRL) level of <10 ng/dl, or a normalized PRL level at a later time point. Results: 30 females and 27 males were included in the study, with a mean age of 33.5 yrs. Median tumor size for the cystic, micro- and macroprolactinomas were 15 mm, 7 mm and 22 mm, respectively. The median duration for DA treatment for the cystic, micro- and macroprolactinoma groups, prior to TSS, were 6, 24 and 12 months, respectively. Median pre-operative PRL levels were lowest with cystic prolactinomas, compared to the micro- and macroprolactinomas at 23.9 ng/ml (Standard deviation (SD)-136.7 ng/ml), 87.9 ng/ml (SD 80 ng/ml) and 229 ng/ml (SD 471.1 ng/ml), respectively (p=0.015). Immediate post-op PRL levels were significantly lower for cystic prolactinomas (n=10, 2.65 ng/ml, SD 4.72 ng/ml) than macroprolactinomas (n=19, 57 ng/ml, SD 159.4 ng/ml) (p=0.025) and for microprolactinomas (n=9.4 ng/ml, SD 3.9 ng/ml) than macroprolactinomas (p=0.030). At the last post-op f/u, no microprolactinoma patient required DA treatment, while 4 patients (24%) with cystic prolactinomas and 18 patients (60%) with macroprolactinomas still required DA therapy. Remission was ultimately achieved in 76% (n=13/17) of surgically-treated cystic prolactinomas, 100% (n=10/10) of microprolactinomas and 23% (n=7/30) of macroprolactinoma patients, at a median f/u of 6, 2.5 and 25 months, respectively. Conclusions: Surgical treatment for cystic prolactinomas, despite their macroadenoma size, resulted in high remission rates (76%), which was comparable to surgically-resected microprolactinomas and superior to macroprolactinomas. This case series supports TSS for this subset of prolactinoma patients. References: 1. Nakhleh A, Shehadeh N, Hochberg I et al., 2018. Management of cystic prolactinomas: a review. Pituitary. 21:425-430. 2. Ogiwara T, Horiuchi T, Nagm A, et al. 2017. Significance of surgical management for cystic prolactinoma. Pituitary 20:225-230.3. Kreutzer J, Buslei R, Wallaschofski H, et al. 2008. Operative treatment of prolactinomas: indications and results in a current consecutive series of 212 patients. Eur J Endocrinol 158:11-18.