The progress of fibroblast activation protein inhibitors PET/computed tomography in the diagnosis and treatment of lymphoma: a narrative review

Lymphoma is a highly heterogeneous hematologic malignancy, for which precise diagnosis and staging are crucial for treatment planning. Although fluorine-18 fluorodeoxyglucose PET/computed tomography (18F-FDG PET/CT) is the current 'gold standard' for imaging evaluation, it has limitations such as lack of cancer specificity and insufficient sensitivity in indolent lymphomas. Isotope-labeled fibroblast activation protein inhibitors (FAPI), such as gallium-68 FAPI (68Ga-FAPI), represent a novel class of radiopharmaceuticals targeting the tumor microenvironment and have shown unique potential in PET/CT imaging for various tumors, including lymphoma. This narrative review compares the imaging characteristics, diagnostic and staging accuracy, and therapeutic value of FAPI PET/CT and 18F-FDG PET/CT in lymphoma by synthesizing existing literature. The results indicate that for most lymphoma subtypes, the overall performance of FAPI PET/CT remains inferior to that of 18F-FDG PET/CT. However, in specific scenarios (e.g. indolent lymphoma, gastrointestinal involvement), it can serve as an important complementary imaging modality and further reveal the molecular characteristics of the tumor. FAPI-based targeted therapy also shows preliminary promise. Overall, current evidence supports FAPI PET/CT as a valuable supplement to 18F-FDG PET/CT in specific clinical contexts. Its definitive clinical role awaits further clarification through more prospective studies.