Comparative Evaluation of 68Ga-FAPI-04 PET for Initial N and M Staging in Gastric Cancer: A Study Against Histopathology and Contrast-Enhanced CT

Purpose: To evaluate the efficiency of 68 Ga-FAPI-04 PET (PET/MRI or PET/CT) for N and M staging in gastric carcinoma and compare outcomes with histopathology and contrast-enhanced computed tomography (CECT). Patients and Methods: Patients with gastric carcinoma who had undergone 68 Ga-FAPI-04 PET/MRI or PET/CT before treatment were retrospectively enrolled. Histopathology post lymphadenectomy was the gold standard for N staging, while histopathology and follow-up data were the reference for overall outcomes. The diagnostic efficiency of 68 Ga-FAPI-04 PET for detecting regional lymph node involvement and distant metastases was compared to that of CECT. Results: Sixty-two patients were enrolled. In 18 patients who underwent 68 Ga-FAPI-04 PET/MRI and lymphadenectomy, 532 lymph nodes were dissected. 68 Ga-FAPI-04 PET/MRI showed similar sensitivity, specificity, and accuracy compared to CECT (28.3% vs. 23.2%, 99.8% vs. 99.3%, and 86.5% vs. 85.2%, all P > 0.05). Fifty-five patients had regional lymph node metastasis, 68 Ga-FAPI-04 PET exhibited comparable diagnostic efficiency to CECT, with sensitivity of 83.6% versus 87.3%, specificity of 100% versus 85.7%, accuracy of 85.5% versus 87.1% (all P > 0.05). Excluding 3 patients with only abdominal CECT, 32 out of 59 patients had distant metastasis, with no significant differences in sensitivity, specificity, and accuracy between 68 Ga-FAPI-04 PET and CECT based on patient (100% vs. 87.5%, 92.6% vs. 96.3%, and 96.6% vs. 91.5%, all P >0.05). Notably, 68 Ga-FAPI-04 PET outperformed CECT in detecting peritoneal, distant lymph nodes, bone, liver, and ovarian metastases by visualizing more lesions or greater lesion extent. Conclusions: 68 Ga-FAPI-04 PET exhibits comparable diagnostic performance to CECT for patient-based N staging and M staging of gastric cancer. However, it surpasses CECT in visualizing distant metastases.