FRI298 Serum Prolactin To Tumor Size Ratio As An Effective Parameter To Accurately Distinguish Prolactinoma From NFPT

Disclosure: I. Mishra: None. A. Pradhan: None. A.K. Baliarsinha: None. Preoperative diagnosis of prolactinomas is critical because dopamine agonists therapy have been regarded as a primary treatment. Multiple studies have compared serum prolactin levels in clinically nonfunctioning (NF) tumors and prolactinomas to identify cutoffs that may distinguish primary tumoral secretion from stalk effect. Prolactin levels are correlated with the size of prolactinomas but are not associated with tumor size in non prolactin-secreting lesions or the degree of stalk deviation and compression. By using the tumor size, we investigated an effective parameter for the discrimination between prolactinoma and NFPT. 33 patients with pituitary lesion of histological diagnosis were retrospectively recruited for this study. The data obtained was entered into Microsoft Excel Worksheet and analysed using Statistical Package for Social Sciences (SPSS, IBM Corp. Released 2020. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.).The Prolactinoma group (n=16) showed higher serum prolactin (mean=418 ng/mL) than those in the NFPT group (n=17) (mean=33.34 ng/mL, p-values < 0.001).Using receiver operating curve analyses, we compared diagnostic performances of serum prolactin (PRL)/ tumor volume ratio in both groups. Unlike NFPT, serum prolactin values significantly correlated with tumor volume in Prolactinoma group. At a cut off of 12.2ng/ml/cm3,serum PRL/tumor volume was found to have a sensitivity of75.8% in diagnosing prolactinomas. However the specificity was 24.2%. Burke et al and Wright et al studied significantly smaller groups of patients and reported a linear relationship between prolactin levels and prolactinoma volume as estimated by a simplified ellipsoid volume equation. Our study demonstrates that the assessment of prolactin secretory density, based on a calculation of serum prolactin per unit tumor volume, can be used as a potential method to distinguish prolactinomas from hyperprolactinemia secondary to stalk effect and could be valuable in guiding patient management in equivocal or challenging patient cases wherein the etiology of hyperprolactinemia is uncertain. Reference: (1) Burke WT, Penn DL, Castlen JP, et al. Prolactinomas and nonfunctioning adenomas: preoperative diagnosis of tumor type using serum prolactin and tumor size. J Neurosurg. 2019:1e8.(2) Wright K, Lee M, Escobar N, et al. Tumor volume improves preoperative differentiation of prolactinomas and nonfunctioning pituitary adenomas.Endocrine.2021;74(1):138e145 Presentation: Friday, June 16, 2023