Abnormal adnexal uptake in ⁶⁸Ga-FAPI PET/CT: from physiological variants to malignant characterization

The adnexal region in females presents complex imaging due to the menstrual cycle. Accurate diagnosis is crucial for effective tumor treatment. This study aims to assess the clinical utility of abnormal adnexal uptake on ⁶⁸Ga-FAPI PET/CT for early and precise lesion characterization.

This study retrospectively analyzed all female patients with abnormal adnexal uptake on ⁶⁸Ga-FAPI PET/CT at our institution from November 2021 to June 2024. Semiquantitative analysis of PET/CT imaging parameters was performed, combined with serum tumor markers and immunohistochemical markers. Pathological findings or imaging follow-up ≥ 6 months served as the gold standard for evaluating the diagnostic performance of ⁶⁸Ga-FAPI PET/CT.

The study included 121 female patients with a mean age of 53.8 ± 12.2 years (18-80 years). A total of 184 adnexal lesions with abnormal uptake were identified. Pathology/follow-up confirmed 82.6% as malignancies, comprising 84 primary and 16 metastatic cases. Additionally, 2 borderline tumors and 19 benign lesions were detected. The positive predictive value was 83.5%. SUVmax differed significantly among primary malignant, metastatic, and benign lesions (12.52 ± 5.41 vs. 9.78 ± 3.39 vs. 5.52 ± 4.17). In the subset of patients with available pathological specimens, SUVmax showed weak to moderate positive correlations with Ki-67 (r = 0.361, p < 0.001) and p53 (r = 0.419, p < 0.001). Notably, the mean SUVmax in the Ki67 > 20% group was significantly higher than in the Ki67 ≤ 20% group (p < 0.001). ROC analysis showed an AUC of 0.85 of SUVmax alone for diagnosing malignant adnexal lesions, increasing to 0.89 when combined with tumor markers.

⁶⁸Ga-FAPI PET/CT demonstrates high diagnostic performance for ovarian lesions. Among pathologically confirmed cases, SUVmax correlates with proliferative activity and malignant potential, supporting its role in diagnostic optimization.