Reversing "Flip-Flop" Phenomenon of 131 I and Glucose Avidity in RET-Fusion Positive Radioiodine-Refractory Thyroid Cancer Lesions After Treatment of Pralsetinib.

ABSTRACT: A 61-year-old man presented with papillary thyroid cancer in radioiodine-refractory status after high-activity 131 I treatments following thyroidectomy. FDG-avid neck and pulmonary metastases but without 131 I-uptake were detected. CCDC6-RET fusion was identified from the tumor lesion. He was treated with pralsetinib, a RET inhibitor, followed by another high-activity 131 I therapy. Posttherapeutic scan displayed restoration of 131 I avidity at those lesions only shown on previous FDG PET/CT. Reduced FDG avidity of those lesions and decreased serum antithyroglobulin antibody titer were also noticed. This case illustrated successfully reinduced 131 I avidity in papillary thyroid cancer through redifferentiation with target therapy to suppress tumor RET overexpression.

Prognostic Value of 18F-FDG PET/CT Volume-Based Metabolic Parameters in Patients with Node-Negative Stage II Esophageal Squamous Cell Carcinoma.

Esophageal squamous cell carcinoma (ESCC) is a major cancer prevalent in Asian males. Pretreatment tumor burden can be prognostic for ESCC. We studied the prognostic value of metabolic parameters of 2-deoxy-2-[18F] fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) and the serum squamous cell carcinoma antigen (SCC-Ag) level in node-negative stage II ESCC patients. Eighteen males underwent staging evaluation were included. The volume-based metabolic parameters derived from 18F-FDG PET/CT, including metabolic tumor volume (MTV) and total lesion glycolysis (TLG), were obtained using the PET Volume Computer Assisted Reading application. The Spearman correlation coefficients were calculated to assess the relationship between metabolic parameters and pretreatment serum SCC-Ag levels. Based on the 5-year follow-up, patients were sub-divided into the demised and the stable groups. Potential prognostic value was assessed by independent t-test and the Mann-Whitney U test. The association of overall survival was assessed using univariate and multivariate Cox regression analyses. The demised group showed significant higher values in serum SCC-Ag, as well as in MTV and TLG, but not SUVmax and SUVmean. The SUVmax, MTV, TLG, and serum SCC-Ag showed significant association with overall survival. Our findings suggest potential usage of pretreatment volume-based metabolic parameters of 18F-FDG PET/CT and serum SCC-Ag as prognostic factors for node-negative stage II ESCC patients.