SAT521 Predictive Value of Tumor Volumetrics in Patients with Medullary Thyroid Cancer

Disclosure: N. Behairy: None. S. Gubbi: None. M.G. Pascoal: None. A. Bharadwaj: None. E.C. Wright: None. T. Abijo: None. N. Uttarkar Vikram: None. P. Veeraraghavan: None. C. Cochran: None. J. Glod: None. J. Klubo-Gwiezdzinska: None. Predictive Value of Tumor Volumetrics in Patients with Medullary Thyroid Cancer Background Medullary thyroid cancer (MTC) is a rare endocrine malignancy that can present either as a sporadic disease or as a part of inherited autosomal dominant multiple endocrine neoplasia type 2A (MEN2A) and 2B (MEN2B) syndromes. There is limited data on the prognostic value of the tumor volume (TV) doubling time (TVDT) in patients with sporadic and familial MTC. Therefore, the goal of this study was to examine the association between TVDT and disease-specific survival (DSS) in patients with metastatic MTC. Material and Methods This cohort study included patients with metastatic MTC for whom at least 3 follow-up CT/MRI scans revealed ≥2 measurable lesions and up to the 5 largest lesions in each affected organ were analyzed. The tumor volumes were measured in 2 dimensions (2D) per standard practice reporting and 3 dimensions (3D) using an ellipsoid formula. The average TVDT of all measured lesions in each organ with metastatic deposits was calculated using a previously reported formula. Calcitonin (Ct-DT) and CEA doubling times (CEA-DT) were assessed using the American Thyroid Association Guidelines calculator. The association between DSS and TVDT, Ct-DT, and CEA-DT was tested using Cox regression. Correlations were assessed using a Spearman correlation coefficient. The study was approved by the Institution Review Board. Results The study cohort consisted of 51 patients (27 women, 53%) with age at the initial scan 24 ± 17 years and an average primary tumor size of 3.3±2.0 cm. Seven patients presented with sporadic MTC, 12 with MEN2A and 32 with MEN2B. During a follow-up of 8.0±4.3 years, 28/51 (55%) patients had disease progression and required systemic or local therapies and 9/51 (18%) patients died. A total of 456 scans were analyzed documenting that the organs with the most rapid TVDT were neck masses in 25/51 (49%), liver metastases in 16/51 (31%), lung nodules in 7/51 (14%) and prostate lesions in 3/51 (6%) patients. There was a strong correlation between 2D and 3D TVDT (r = 0.96) as well as between Ct-DT and CEA-DT (r = 0.82). However, the correlation between 2D TVDT and Ct-DT and CEA-DT were low (r = 0.45 for both). The DSS hazard ratios (HR) for DT <1 year compared to ≥3 years were 8.2 (1.5-45.4) for 2D TVDT, 8.7 (1.6-48.2) for 3D TVDT, 15.9 (1.72-146.7) for Ct-DT, and 11.72 (2.0-68.7) for CEA-DT. DSS was not associated with either familial or sporadic etiology of MTC (p = 0.38), gender (p = 0.12), or age at initial scan (p = 0.85). Conclusions Apart from Ct-DT and CEA-DT, TVDT is a valuable prognostic factor in metastatic MTC. Given a strong correlation between 2D and 3D TVDT, standard 2D-based TVDT measurements might be used as an easily obtained and clinically feasible prognostic marker of DSS in MTC patients. Presentation Date: Saturday, June 17, 2023