Tomografía por emisión de positrones en sarcomas

Sarcomas are rare, heterogeneous tumors of mesenchymal origin. Molecular imaging is crucial for diagnosis, staging, and therapy monitoring. ¹⁸F‑Fluorodeoxyglucose (¹⁸F‑FDG) positron-emission tomography/computed tomography (PET/CT) is a powerful technique for imaging high-grade soft tissue and bone sarcomas and supports staging, grading, biopsy targeting, and risk assessment using standardized criteria, e.g., European Organization for Treatment of Cancer (EORTC) criteria and PET Response Criteria in Solid Tumors (PERCIST).

Fibroblast activation protein (FAP) is expressed at high concentrations in many sarcomas, often directly on the tumor cells themselves as well as on cancer-associated fibroblasts. FAP is therefore an attractive target for molecular imaging and therapy. ⁶⁸Ga-labeled FAP inhibitors (FAPIs) have shown higher uptake compared to ¹⁸F‑FDG across all sarcoma subtypes, including those with low ¹⁸F‑FDG avidity. FAPI-PET shows favorable tumor-background contrast and strong correlation with histopathological FAP expression. Prospective studies suggest that FAPI-PET may be superior to ¹⁸F‑FDG-PET in certain histological subtypes and may identify candidates for FAP-targeted radioligand therapy (RLT). Early clinical experience with radioligands such as ⁹⁰Y‑FAPI-46 demonstrates safety, feasibility, and disease control under FAP-RLT in more than half of evaluable patients with advanced metastatic sarcoma.

Further prospective studies are needed to evaluate and establish the role of ¹⁸F‑FDG and FAPI-PET in personalized treatment strategies and sarcoma management.