Comparison of 68Ga-FAPI PET/CT and 18FDG PET/CT Modalities in Gastrointestinal System Malignancies with Peritoneal Involvement.

PURPOSE: In this study, we aimed to investigate the utilization of 68Ga-FAPI PET/CT in comparison to 18FDG PET/CT to evaluate the peritoneal involvement of the gastrointestinal malignancies alongside primary lesions and other metastatic foci. PROCEDURES: A total of 37 patients with various gastrointestinal malignancies with accompanying peritoneal involvement who underwent 68Ga-FAPI PET/CT and 18FDG PET/CT imaging between September 2020 and June 2021 were included in this retrospective study. SUVmax values of 68Ga-FAPI and 18FDG were compared according to lesion locations. Also, the lesion localization ability of both imaging was compared in patient basis. RESULTS: Of the 37 patients with peritoneal involvement (23 males and 14 females; median age, 62.8 ± 12.7 years), 35.1% (n = 13) had colorectal cancer, 37.8% (n = 14) gastric cancer, and 27.0% (n = 10) pancreaticobiliary cancer. While 45.9% of them were operated, the remaining did not have surgery. The mean time interval between two studies was 3.2 days (range: 2-6 days). The mean SUVmax value of peritoneal metastases (p < 0.001) was significantly higher with 68Ga-FAPI PET/CT compared to that with 18FDG PET/CT, as in primary lesions (p < 0.001), lymph node metastases (p = 0.006), liver metastases (p = 0.002), and bone metastases (p = 0.018). A total of 185 lesions was detected in the initial assessment with 18FDG PET/CT. Of the total lesions detected with 18FDG PET/CT, 5 of them were evaluated as benign lesions with 68Ga-FAPI PET/CT also in accordance with the reference standard. In addition to 180 lesions detected with 18FDG PET/CT, a total of 37 additional malignant lesions, 12 of which were peritoneal metastases, were detected with 68Ga-FAPI PET/CT. CONCLUSION: 68Ga-FAPI PET/CT was determined to be superior to 18FDG PET/CT in terms of detection of peritoneal involvement with high image quality as well as primary tumor and other metastatic foci. Consequently, 68Ga-FAPI PET/CT can be used as a complementary imaging modality especially for inconclusive 18FDG findings due to the lack of accuracy of 18FDG PET/CT in some of the metastatic regions, especially in the liver.

Comparison of [68Ga]-FAPI PET/CT and [18F]-FDG PET/CT in Multiple Myeloma: Clinical Experience.

OBJECTIVE: In this study, we aimed to compare [68Ga]FAPI PET/CT and [18F]FDG PET/CT imaging to detect lesions in multiple myeloma. METHODS: A total of 14 patients with multiple myeloma who underwent [68Ga]FAPI PET/CT and [18F]FDG PET/CT imaging were included in this retrospective study. SUVmax values of [68Ga]FAPI and [18F]FDG were compared according to lesion locations. Also, lesion localization ability of both imaging methods was compared on the patient basis. RESULTS: In 4 of 14 patients, [68Ga]FAPI PET/CT and [18F]FDG PET/CT have not detected any bone lesions. In 8 of the remaining 10 patients [18F]FDG PET/CT detected bone lesions but in this group, 6 patients showed more higher SUVmax values than [18F]FDG PET/CT in [68Ga]FAPI PET/CT.In contrast, 2 of 8 patients showed more higher SUVmax values than [68Ga]FAPI PET/CT in [18F]FDG PET/CT. Moreover, [68Ga]FAPI PET/CT detected bone lesions in two patients, which werenot detected by [18F]FDG PET/CT. Also, in five patients, [68Ga]FAPI PET/CT showed more bone lesions in comparison with[18F]FDG PET/CT. Only one patient, [18F]FDG PET/CT showed more bone lesions. Three extramedullary involvements were observed in the following locations: lung, presacral lymph node, and soft tissue mass lateral to the right maxillary sinus. Among these involvements, higher SUVmax values were observed in the lung and presacral lymph node with [68Ga]FAPI compared to [18F]FDG. However, the soft tissue mass showed a higher SUVmax value in [18F]FDG than [68Ga]FAPI. CONCLUSIONS: No significant superiority was observed in [68Ga]FAPI PET/CT over [18F]FDG PET/CT in patients with MM. However, [68Ga]FAPI PET/CT can be utilized as a complementary imaging method to [18F]FDG PET/CT in some settings, especially in low-[18F]FDG affinity and inconclusive cases. Considering the favorable aspects of [68Ga]FAPI PET/CT in MM, such as low background activity, absence of non-specific bone marrow, and physiological brain involvement, further studies with a larger sample size should be conducted.

Superiority of 68Ga-FAPI PET/CT scan in detecting additional lesions compared to 18FDG PET/CT scan in breast cancer.

PURPOSE: We compared the ability of 68Ga-FAPI PET//CT with 18FDG PET/CT imaging techniques to detect additional lesions in breast cancer patients that may affect further chemotherapy options. METHODS: A total of 48 patients with breast cancer underwent concurrent 68Ga-FAPI-04 and 18FDG PET/CT regardless of whether they had received chemotherapy or not in the last month before imaging. Both modalities were compared according to various parameters: clinical/pathological features, number of lesions detected, activity uptake (SUVmax), and the effect on the evaluation of response to treatment in the post-chemotherapy group. RESULTS: This retrospective study included 48 patients with breast cancer (mean age 53.3 ± 11.7 years; IDC 89.6%; ILC 10.4%). In the comparison of both modalities, no statistical significance was obtained in terms of the pathological characteristics of the patients. More lesions were demonstrated in all categorized regions in 68Ga-FAPI PET/CT imaging with higher uptake values compared to 18FDG PET/CT in this study. In the treatment response evaluation of the post-chemotherapy group, 12 cases (12/24) who were evaluated as PMR, CMR, or SD according to 18FDG PET/CT results were later accepted as PD due to newly detected lesions in complementary 68Ga-FAPI PET/CT imaging and treatment of patients was managed accordingly by clinicians. CONCLUSION: It was determined that 68Ga-FAPI PET/CT was superior to 18FDG PET/CT in terms of accuracy and it was thought that 68Ga-FAPI PET/CT could be utilized as an additional complementary imaging to 18FDG PET/CT. Moreover, 68Ga-FAPI PET/CT, with its significant theranostic potential, could become a key element in predicting the pathological response of breast cancer patients in further researches.