Comparative Evaluation of [68Ga]Ga-FAPI-04 PET Versus Conventional Imaging for Peritoneal Carcinomatosis Detection in Ovarian Carcinoma: A Multimodal Imaging Study.

Accurate preoperative assessment of peritoneal tumor burden and distribution is vital for patient selection, as it reduces the need for diagnostic laparoscopy, prevents futile surgical interventions in nonresectable cases, and streamlines the therapeutic approach of primary surgery or neoadjuvant treatment. This study compared the diagnostic performance of [68Ga]Ga-FAPI-04 PET/CT (FAPI PET) with that of contrast-enhanced CT (ceCT) for the detection of peritoneal carcinomatosis. Methods: Two hundred patients with primary epithelial ovarian carcinoma underwent whole-body FAPI PET and abdominopelvic ceCT before cytoreductive surgery. The extent of peritoneal carcinomatosis was quantified using the Peritoneal Cancer Index (PCI) across 13 regions, categorized into 4 anatomic areas (pelvis, upper abdomen, central region, and small bowel with mesentery). The sensitivity, specificity, and accuracy of each modality were evaluated against intraoperative assessment as the gold standard. Results: In this study, data from 200 patients with primary ovarian carcinoma were analyzed. The mean age of participants was 56.4 ± 12.72 y. The mean PCI was 14.14 for FAPI PET, 10.8 for ceCT, and 15.77 intraoperatively. Both FAPI PET and ceCT showed strong correlation with surgical PCI (r = 0.829 and 0.805), with no significant difference in global PCI correlation. However, in the small-bowel region, FAPI PET demonstrated higher correlation than ceCT (r = 0.810 vs. 0.664, P = 0.0237). FAPI PET achieved sensitivity, specificity, and accuracy of 81.8%, 89.3%, and 86.0%, respectively, whereas ceCT yielded 54.6%, 96.4%, and 78.0%, respectively. Regionally, FAPI PET demonstrated higher sensitivity in the upper abdomen (76.5% vs. 23.5% for ceCT) and small bowel (50% vs. 31.3% for ceCT), whereas both modalities performed comparably in the pelvis (59% vs. 63.6% for ceCT) and central abdomen (68.4% vs. 52.6% for ceCT). Conclusion: FAPI PET significantly outperformed ceCT in diagnostic sensitivity and PCI estimation, particularly in surgically challenging regions, such as the small bowel and upper abdomen. These findings, along with the noninvasive nature and independence from glucose metabolism, support the incorporation of FAPI PET into routine preoperative evaluation to enhance surgical planning and improve treatment stratification in patients with advanced ovarian cancer.