6454 Identifying Gaps in Obtaining Germline RET Testing for Patients with Medullary Thyroid Cancer

Abstract Disclosure: A.N. Lim: None. J. Comeaux: None. C. Ricker: None. K.S. Wei: None. T.E. Angell: None. Background: Medullary thyroid carcinoma (MTC) occurs sporadically or from germline pathogenic variants of the RET proto-oncogene in multiple endocrine neoplasia type 2 (MEN2). Current ATA guidelines recommend germline RET testing in all patients with C-cell hyperplasia or MTC. Because disparities may exist in the implementation of this recommendation, we analyzed records of patients with MTC to identify variables associated with germline RET testing. Methods: Patients with MTC were identified from a cohort study of all adult patients undergoing thyroid surgery from 2015-2022 at two affiliated academic centers: a private hospital or a safety-net hospital. Patients were categorized as RET-tested or not RET-tested. Data collection included: patient age, gender, ethnicity, nodule and lymph nodule findings on ultrasound (US), calcitonin and CEA levels, and surgical pathology results. Medical reports were reviewed for reasons that RET testing was or was not obtained. Results: Of 24 MTC patients, 50% were female, mean age ± SD was 50.8 ± 12.3, and 15 (62.5%) had Hispanic ethnicity. RET testing was performed in 14 (58.3%) patients and 3 (21.4%) had a pathogenic variant. RET-tested patients had a median nodule size of 3.45 cm (IQR 2.40-4.53) vs. 2.40 cm (IQR 0.98-3.25) in not-RET tested patients (p<0.05). There were no significant differences between groups in age, gender, ethnicity, preoperative US findings, preoperative calcitonin or CEA levels, or histopathologic status. RET testing was performed in 11/14 (78.6%) patients at the private hospital vs. only 5/10 (50.0%) patients at the safety-net hospital (p=0.20). Considering this, we further investigated the use of RET testing in the initial management of MTC patients. RET testing was performed or planned during initial management in 13/14 (92.9%) patients at the private hospital vs. only 5/10 (50%) patients at the safety-net hospital (p=0.05). At the private hospital, RET testing was requested for apparent sporadic disease (n=11), family history of MTC (n=1), and coexistent pheochromocytoma (n=1). At the safety-net hospital, RET testing was requested for apparent sporadic disease (n=4) and family history of MTC (n=1), but reportedly was not pursued in 5 patients because MTC appeared to be sporadic. Discussion: In this cohort of patients with MTC, larger nodule size was significantly associated with the rate of germline RET testing. Larger MTC tumor size alone may have prompted greater attention to germline testing, but also may have been associated with other findings, which could be further assessed with a larger sample size by multivariable analysis. The disparity in RET testing as part of initial management at the safety-net hospital may be multifactorial, but future analyses should explore provider decision-making, as well as facility and patient variables. Presentation: 6/1/2024