Published by Bioscientifica Ltd. Printed in Great Britain © 2020 European Society of Endocrinology https://eje.bioscientifca.com https://doi.org/10.1530/EJE-19-0753 European Journal of Endocrinology 182:2 177–183 D Kim and others PRL cut-ofs and tumor size reduction Prolactin ≤1 ng/mL predicts macroprolactinoma reduction after cabergoline therapy Daham Kim, Cheol Ryong Ku, Kyungwon Kim, Hyein Jung and Eun Jig Lee Department of Internal Medicine, Institute of Endocrine Research, Yonsei University College of Medicine, Seoul, Korea Abstract Objective: The association between prolactin level variation and prolactinoma size reduction remains unclear. This study aimed to determine the prolactin level cut-of predictive of a tumor size reduction. Design: Retrospective cohort study. Methods: We reviewed medical records of patients with prolactinoma who received primary cabergoline therapy and for whom complete data on pituitary hormone assays and sellar MRI at baseline and 3 months post treatment were available. We tested whether the certain prolactin level after 3 months post treatment predicted better response. Results: Prolactin levels normalized in 109 (88.6%) of 123 included macroprolactinoma patients. The mean tumor size reduction was 22.9%, and patients in the lowest prolactin tertile (≤0.7) had the highest frequency of tumor size reductions of ≥20% (73.7 vs 52.9% and 45.9% in tertiles 2 (>0.7 to 2.6) and 3 (>2.6 to 20), P = 0.015). Patients with prolactin levels ≤1 ng/mL exhibited larger tumor size reductions vs those with prolactin levels of 1–20 (27.2 ± 18.3% vs 19.5 ± 13.9%, P = 0.014), 1–10 (19.3 ± 13.7%, P = 0.017) and 1–5 ng/mL (19.2 ± 14.3%, P = 0.039). A multivariable logistic regression analysis revealed that a prolactin level ≤1 ng/mL at 3 months and high-dose cabergoline therapy were signifcantly associated with tumor size reductions of ≥20% (odds ratio (OR): 2.8, 95% confdence interval (CI): 1.2–6.7, P = 0.017; OR: 2.0, 95% CI: 1.0–3.9, P = 0.043). Conclusions: A prolactin level ≤1 ng/mL at 3 months after cabergoline treatment was correlated with a signifcant tumor size reduction in patients with macroprolactinoma. This fnding may help clinical decision making when treating macroprolactinoma patients. Introduction Prolactinomas are the most commonly occurring pituitary adenomas, accounting for approximately 40% of all pituitary tumors and 50–60% of all functional pituitary tumors (1). These tumors cause headaches, visual dysfunction, hypopituitarism, and hyperprolactinemia (2). Patients with prolactinoma typically exhibit the clinical features of hyperprolactinemia, including gonadal dysfunction, amenorrhea, and galactorrhea. Serum prolactin level normalization and tumor shrinkage are the major goals of prolactinoma treatment. The frst line of therapy involves medical management with dopamine agonists such as bromocriptine and cabergoline. Surgical resection is generally reserved for patients who are unresponsive or intolerant to medical therapy. Cabergoline, a specifc D2 receptor agonist, is the frst choice of treatment because of its superior effcacy and better tolerability (3). The recommended cabergoline dosage for initiation is 0.25–0.5 mg twice a week, whereas the usual weekly maintenance doses range from 0.25 to 3.0 mg (4). Correspondence should be addressed to C R Ku Email CR079@yuhs.ac European Journal of Endocrinology (2020) 182, 177–183 Clinical Study Downloaded from Bioscientifica.com at 01/05/2023 03:48:05PM via free access