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Dynamic PET/CT Imaging of ⁶⁸Ga-FAPI-04 in Chinese Subjects.

ABSTRACT: This study aims to further explore dynamic ⁶⁸Ga-FAPI-04 PET/CT imaging of healthy Chinese subjects and lung cancer patients. Moreover, the variability of ⁶⁸Ga-FAPI-04 uptake in normal organs was measured to provide a basis for analyzing its biological distribution, interpreting auxiliary images, determining the reliability of image quantification, and monitoring treatment. Six patients (3 subjects without tumors and 3 lung cancer patients) separately underwent ⁶⁸Ga-FAPI-04 and 2-[¹⁸F]FDG PET/CT imaging within 1 week. The biodistribution and internal radiation dosimetry were reported and compared with data previously obtained from Caucasian patients. Moreover, the mean SUV (standardized uptake value) was normalized to body mass or to lean body mass (SUL), and the coefficients of variation (CVs) were calculated and compared for each volume of interest. The average whole-body effective dose was calculated to be 1.27E-02 mSv/MBq, which was comparable with previously reported results of ⁶⁸Ga-FAPI-04 probes. Furthermore, the SUVmean was slightly higher than the SULmean in most organs; however, the CV of the SULmean for most organs was higher than that of the SUVmean at later time points. In the liver, the CV of the SUVmean was lower (12.7%) than that of the SULmean and was similar to the CV for corresponding 2-[¹⁸F]FDG PET/CT value (11.8%). In addition, ⁶⁸Ga-FAPI-04 PET/CT showed good efficacy for diagnosing lung cancer patients in this study. A comparison of the radiation dosimetry obtained before from a Caucasian population demonstrated no clinically significant differences between these two populations after ⁶⁸Ga-FAPI-04 injection. The variability in most organs was slightly lower for SUVmean than for SULmean, suggesting that SUVmean may be the preferable parameter for quantifying images obtained with ⁶⁸Ga-FAPI-04. In addition, ⁶⁸Ga-FAPI-04 PET/CT imaging is expected to be a promising tool for diagnosing lung cancer.

SUBMITTER: Wang S

PROVIDER: S-EPMC7991833 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose68Ga-FAPI (fibroblast activation protein inhibitor) is a novel and highly promising radiotracer for PET/CT imaging. The aim of this retrospective analysis is to explore the potential of FAPI-PET/CT in gynecological malignancies. We assessed biodistribution, tumor uptake, and the influence of pre- or postmenopausal status on tracer accumulation in hormone-sensitive organs. Furthermore, a comparison with the current standard oncological tracer 18F-FDG was performed in selected cases.Patients and methodsA total of 31 patients (median age 59.5) from two centers with several gynecological tumors (breast cancer; ovarian cancer; cervical cancer; endometrial cancer; leiomyosarcoma of the uterus; tubal cancer) underwent 68Ga-FAPI-PET/CT. Out of 31 patients, 10 received an additional 18F-FDG scan within a median time interval of 12.5 days (range 1-76). Tracer uptake was quantified by standardized uptake values (SUV)max and (SUV)mean, and tumor-to-background ratio (TBR) was calculated (SUVmax tumor/ SUVmean organ). Moreover, a second cohort of 167 female patients with different malignancies was analyzed regarding their FAPI uptake in normal hormone-responsive organs: endometrium (n = 128), ovary (n = 64), and breast (n = 147). These patients were categorized by age as premenopausal (<35 years; n = 12), postmenopausal (>65 years; n = 68), and unknown menstrual status (35-65 years; n = 87), followed by an analysis of FAPI uptake of the pre- and postmenopausal group.ResultsIn 8 out of 31 patients, the primary tumor was present, and all 31 patients showed lesions suspicious for metastasis (n = 81) demonstrating a high mean SUVmax in both the primary (SUVmax 11.6) and metastatic lesions (SUVmax 9.7). TBR was significantly higher in 68Ga-FAPI compared to 18F-FDG for distant metastases (13.0 vs. 5.7; p = 0.047) and by trend for regional lymph node metastases (31.9 vs 27.3; p = 0.6). Biodistribution of 68Ga-FAPI-PET/CT presented significantly lower uptake or no significant differences in 15 out of 16 organs, compared to 18F-FDG-PET/CT. The highest uptake of all primary lesions was obtained in endometrial carcinomas (mean SUVmax 18.4), followed by cervical carcinomas (mean SUVmax 15.22). In the second cohort, uptake in premenopausal patients differed significantly from postmenopausal patients in endometrium (11.7 vs 3.9; p < 0.0001) and breast (1.8 vs 1.0; p = 0.004), whereas no significant difference concerning ovaries (2.8 vs 1.6; p = 0.141) was observed.ConclusionDue to high tracer uptake resulting in sharp contrasts in primary and metastatic lesions and higher TBRs than 18F-FDG-PET/CT, 68Ga-FAPI-PET/CT presents a promising imaging method for staging and follow-up of gynecological tumors. The presence or absence of the menstrual cycle seems to correlate with FAPI accumulation in the normal endometrium and breast. This first investigation of FAP ligands in gynecological tumor entities supports clinical application and further research in this field.

Project description:Bone and soft-tissue sarcomas express fibroblast activation protein (FAP) on tumor cells and associated fibroblasts. Therefore, FAP is a promising therapeutic and diagnostic target. Novel radiolabeled FAP inhibitors (e.g., 68Ga-FAPI-46) have shown high tumor uptake on PET in sarcoma patients. Here, we report the endpoints of the 68Ga-FAPI PET prospective observational trial. Methods: Forty-seven patients with bone or soft-tissue sarcomas undergoing clinical 68Ga-FAPI PET were eligible for enrollment into the 68Ga-FAPI PET observational trial. Of these patients, 43 also underwent 18F-FDG PET. The primary study endpoint was the association between 68Ga-FAPI PET uptake intensity and histopathologic FAP expression analyzed with Spearman r correlation. Secondary endpoints were detection rate, positive predictive value (PPV), interreader reproducibility, and change in management. Datasets were interpreted by 2 masked readers. Results: The primary endpoint was met, and the association between 68Ga-FAPI PET uptake intensity and histopathologic FAP expression was significant (Spearman r = 0.43; P = 0.03). By histopathologic validation, PPV was 1.00 (95% CI, 0.87-1.00) on a per-patient and 0.97 (95% CI, 0.84-1.00) on a per-region basis. In cases with histopathologic validation, 27 of 28 (96%) confirmed patients and 32 of 34 (94%) confirmed regions were PET-positive, resulting in an SE of 0.96 (95% CI, 0.82-1.00) on a per-patient and 0.94 (95% CI, 0.80-0.99) on a per-region basis. The detection rate on a per-patient basis in 68Ga-FAPI and 18F-FDG PET was 76.6% and 81.4%, respectively. In 8 (18.6%) patients, 68Ga-FAPI PET resulted in an upstaging compared with 18F-FDG PET. 68Ga-FAPI PET readers showed substantial to almost perfect agreement for the defined regions (Fleiss κ: primary κ = 0.78, local nodal κ = 0.54, distant nodal κ = 0.91, lung κ = 0.86, bone κ = 0.69, and other κ = 0.65). Clinical management changed in 13 (30%) patients after 68Ga-FAPI PET. Conclusion: We confirm an association between tumoral 68Ga-FAPI PET uptake intensity and histopathologic FAP expression in sarcoma patients. Further, with masked readings and independent histopathologic validation, 68Ga-FAPI PET had a high PPV and sensitivity for sarcoma staging.

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Dynamic PET/CT Imaging of ⁶⁸Ga-FAPI-04 in Chinese Subjects.

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Dynamic PET/CT Imaging of 68Ga-FAPI-04 in Chinese Subjects.

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Dynamic PET/CT Imaging of ⁶⁸Ga-FAPI-04 in Chinese Subjects.