The diagnostic value of [18F]F-NOTA-FAPI PET/CT in suspected recurrent ovarian cancer with CA125 dynamic increase level but negative conventional imaging findings.

PURPOSE: We aimed to explore the diagnostic value of [18F]F-NOTA-FAPI-FUSCC-07 ([18F]F-NOTA-FAPI) PET/CT in suspected recurrence ovarian cancer with CA125 dynamic rising but negative conventional imaging findings. METHODS: Forty-one suspected recurrent ovarian cancers who experienced [18F]F-NOTA-FAPI PET/CT for further diagnosis because of continuously rising CA125 value but negative conventional imaging (CT, MR or [18F]FDG PET/CT) findings were enrolled from June 2022 to January 2024. All conventional and [18F]F-FAPI PET/CT scans were performed in sequence within one week. Clinical characteristics, treatment data, [18F]F-NOTA-FAPI PET/CT findings, and survival outcomes were recorded. Differences in [18F]F-NOTA-FAPI PET/CT parameters across CA125 levels were analyzed using the Mann-Whitney U test. RESULTS: [18F]F-NOTA-FAPI PET/CT was positive in 34 patients (82.93%). Lesions were primarily peritoneal (85.29%), followed by lymph nodes (23.53%), stomach (8.82%), and small intestine (2.94%). Prior to imaging, median CA125 level was 51.90 (9.12–1586.00) U/mL, with a rising rate of 0.45 (0.02–44.42) U/mL/day and a doubling time of 56.28 (6.18-613.14) days. Detection rates were higher in the high-CA125 group (positive: 88.24%, negative: 11.76%) compared to the low-CA125 group (positive: 79.17%, negative: 20.83%). Notably, diagnostic performance was superior in patients with CA125 levels between 35 and 70 U/mL. Among 7 FAPI-negative patients, 3 were true-negative and 4 were false-negative. Disease relapse occurred in 30 patients (73.17%) after treatment, with a median PFS of 11.99 months (0-29.2). PFS differed significantly between FAPI-positive and FAPI-negative groups (p = 0.016). CONCLUSIONS: [18F]F-NOTA-FAPI PET/CT demonstrated superior diagnostic performance in ovarian cancer patients with rising CA125 levels and negative conventional imaging findings, particularly in those with CA125 levels between 35 and 70 U/mL.