Comparison of 68Ga-FAPI-04 PET/CT with CECT in the evaluation of peritoneal metastases from gastrointestinal cancers and impact on clinical decision-making

To investigate the diagnostic accuracy of 68Ga-FAPI-04 PET/CT for peritoneal metastasis in gastrointestinal cancers and to assess its impact on clinical decision-making, comparing to contrast-enhanced computed tomography (CECT). We retrospectively included consecutive patients with gastrointestinal cancers, admitted between April 2022 and October 2022, and underwent both 68Ga-FAPI-04 PET/CT and CECT within two weeks. The reference standard was histopathology or imaging follow-up. We compared patient-level accuracy to detect peritoneal metastases and to measure peritoneal tumor burden between 68Ga-FAPI-04 PET/CT and CECT. We assessed the impact of 68Ga-FAPI-04 PET/CT on treatment through a simulated multidisciplinary tumor board. We included 57 patients, among which, 34 (59.65%) had peritoneal metastasis. 68Ga-FAPI-04 PET/CT showed superior sensitivity (97.06% vs. 64.71%) and specificity (95.65% vs. 78.26%) than CECT, as well as area under the curve (0.964 vs. 0.715, P < 0.001). Among patients with peritoneal metastasis, 68Ga-FAPI-04 PET/CT revealed higher peritoneal tumor burden than CECT (peritoneal cancer index [PCI]-region: 6.5 vs. 1, P < 0.001). 68Ga-FAPI-04 PET/CT findings led to changes of treatment in 17 (29.82%) patients, among which, nine (15.8%) patients had new findings related to peritoneum. The impact was deemed high in 10 (17.54%) patients, moderate in six (10.53%), and low in one (1.75%). 68Ga-FAPI-04 PET/CT has the potential to influence clinical decision-making in gastrointestinal cancers and has superior accuracy than CECT. Further studies are warranted to support routine use.