Fibroblast Activation Protein Inhibitor PET Imaging in Head and Neck Cancer.

68Ga-fibroblast activation protein inhibitor (FAPI)-PET is highly promising for head and neck cancers including oral squamous cell carcinomas, hypopharynx carcinomas, adenoid cystic carcinomas, thyroid cancer, and cervical cancer of unknown primary. For oral squamous cell carcinomas, hypopharynx carcinomas, and adenoid cystic carcinomas, 68Ga-FAPI-PET has high potential for the assessment of primary tumors with impact on radiotherapy planning. 68Ga-FAPI-PET can be applied for staging of metastasized thyroid carcinomas. To date, the data on cervical cancer of unknown primary are sparse but highly interesting as 68Ga-FAPI-PET may detect a significant portion of 18fluoro-deoxyglucose-PET-negative primary tumors.