SUN-267 Diagnostic Performance of Parathyroid 4D-CT in MEN1 Syndrome-Associated Primary Hyperparathyroidism

Abstract Disclosure: A. Sharma: None. N. Chakrabarty: None. V. Patil: None. H. Thakkar: None. P. Badhe: None. M. Garale: None. K. Ambulkar: None. S. Memon: None. A. Lila: None. M. Karlekar: None. R. Barnabas: None. T. Pai: None. T. Bandgar: None. Background: In multiple endocrine neoplasia type 1 (MEN1) related primary hyperparathyroidism (PHPT), recognition of asynchronous parathyroid involvement has led to consideration for targeted surgical approaches that require accurate preoperative localization modalities. However, data on parathyroid 4-dimensional computed tomography (4D-CT) in this context remains scarce. Objectives: To assess 4D-CT diagnostic performance in MEN1 PHPT and report outcomes of parathyroidectomy where surgical extent was tailored as per the CT findings. Study setting: Retrospective study in an endocrine referral center where 4D-CT is routinely used as first-line imaging for parathyroid localization. Methods: CT scans of MEN1 PHPT patients from Jan 2008–Dec 2022 (20% clinical, 80% genetic diagnosis) were independently reviewed by two radiologists (15 and 11 years of experience) aware of MEN1 but blinded to original radiology reports, clinical/surgical details, histopathology, and outcomes. The per-patient analysis included the entire cohort. The per-lesion analysis was limited to operated patients, where pathology and surgical outcomes served as the gold standard. Results: Among 60 MEN1 PHPT patients, 43% were symptomatic and 93% had hypercalcemia at the time of CT (median calcium 11.7 mg/dL, PTH 248 pg/mL). The per-patient analysis included 61 4D-CT scans (53 previously unoperated, 8 for persistent/recurrent PHPT). The original report and radiologists identified abnormal glands in 96.7-100% of patients (mean 2.25 lesions per patient in unoperated, 1.71 in persistent/recurrent). In the per-lesion analysis (n=33), 4D-CT had 85-89.5% sensitivity and 90-94% specificity, outperforming ultrasonography and Sestamibi scan (P<0.001 for both). There was good inter-observer agreement on CT for lesion quadrant localization in the overall cohort and operated subgroup (Cohen’s kappa 0.64-0.91). In 24/33 patients, only CT-identified abnormal glands were resected, while glands not seen on CT were left unexplored (imaging-guided group). The remaining 9 had bilateral neck exploration (BNE) with subtotal/total parathyroidectomy and autotransplantation, regardless of CT findings. Both imaging-guided and BNE groups had similar baseline characteristics and number of lesions identified per patient on 4D-CT. The imaging-guided group had more adenomas and fewer hyperplasia (35% vs. 64%; P<0.001) and normal glands (2% vs. 17%; P=0.01) on pathology than BNE. Despite resecting fewer glands per patient (P<0.001), the imaging-guided group had comparable remission (91.7% vs 100%) and recurrence rates (9.5% vs 0%; P=1.00) to the BNE group over similar follow-up duration, with lower permanent hypoparathyroidism (4 vs. 44%; P=0.01). Conclusion: 4D-CT demonstrated good diagnostic performance and facilitated favorable operative outcomes in MEN1 PHPT, supporting its role in planning surgical extent. Presentation: Sunday, July 13, 2025