Comparação do desempenho do 18F-FDG e 18F-FES PET/CT no rastreamento de metástases à distância em pacientes com câncer de mama receptor hormonal positivo

Abstract

Introduction: 16α-18F-fluoro-17β-estradiol (FES) is an estrogen receptor (ER)-specific radiopharmaceutical with several potential applications that remain underexplored. Objective: To compare the performance of positron emission tomography/computed tomography (PET/CT) using FES and fluorine-18 labeled fluorodeoxyglucose (FDG) in the detection of distant metastases in patients with hormone receptor-positive (HR+) breast cancer. Methods: This prospective study included 31 patients with HR+ breast cancer at clinical stage IIb or higher who had not yet undergone treatment. Each patient underwent two PET/CT scans (one with FES and one with FDG), performed within an interval of up to seven days. Statistical analyses were conducted on the collected data. Results: FDG-PET/CT identified a higher absolute number of avid lesions compared to FES-PET/CT, although without statistical significance (p = 0.523), and demonstrated comparable sensitivity in the central nervous system (CNS) and superior sensitivity in the liver, lungs, and bones. On the other hand, FES-PET/CT showed higher overall specificity than FDG-PET/CT, particularly in distant lymph nodes and the lungs. High ER expression was associated with a greater number of lesions detected by FES-PET/CT (p = 0.048). FDG-PET/CT detected fewer lesions in cases of high ER expression (p = 0.032). Clinical staging did not significantly correlate with the number of identified metastatic lesions. Prognostic staging, however, showed a significant association with metastatic burden detected by FES-PET/CT (p = 0.037). ROC curve analysis allowed the establishment of optimal SUVmax cutoff points for each site in this cohort, and the Youden index helped identify the SUVmax threshold with the highest discriminatory power, especially for lymph nodes, lungs, and bones. Conclusion: Neither method demonstrated globally superior performance. The choice between them can be individualized, taking into account the clinical context, tumor molecular profile, and diagnostic purpose. In selected scenarios, combined use of both scans may optimize systemic staging accuracy and enhance therapeutic decision-making in HR+ breast cancer.