Role of 68 Ga FAPI PET-CT Versus 18 F-FDG PET-CT in the Diagnostic Evaluation of Poorly Cohesive Gastric Carcinomas

Poorly cohesive carcinoma (PCC) of the stomach is a rare and aggressive gastric cancer (GC) with high metastasis rates and poor prognosis. Traditional imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and endoscopy often lack sufficient sensitivity for detecting both primary tumours and metastases. Recently, Gallium 68 ( 68 Ga)-fibroblast activation protein inhibitor (FAPI) Positron Emission Tomography and Computed Tomography (PET-CT) has emerged as a promising imaging modality due to its high affinity for fibroblast activation protein, which is expressed in various solid tumours, including GC. This case series aims to evaluate the role of 68 Ga-FAPI PET/CT in detecting primary tumours, nodal and distant metastases, and assessing treatment response in PCC of the stomach. We present three cases of PCC, where patients underwent 68 Ga-FAPI PET/CT for diagnosis, staging, restaging, and posttreatment follow-up. The findings from 68 Ga-FAPI PET/CT were compared with those obtained from 18 F-fluorodeoxyglucose PET/CT. In all cases, 68 Ga-FAPI PET/CT demonstrated superior sensitivity in detecting both primary tumours and metastatic sites, providing valuable insights, particularly in cases with suspected peritoneal or lymph node involvement. Moreover, 68 Ga-FAPI PET/CT was instrumental in assessing treatment response and detecting recurrence, offering more accurate tumour burden evaluation than traditional imaging. 68 Ga-FAPI PET/CT appears to be a promising imaging tool in the clinical management of PCC of the stomach. It enhances the detection of primary and metastatic disease, offers precise assessment of tumour burden, and may help guide therapeutic decisions, especially in advanced-stage disease.