Klinik und Poliklinik für Hals-, Nasen- und Ohrenkrankheiten, plastische und ästhetische Operationen
Refine
Has Fulltext
- yes (3)
Is part of the Bibliography
- yes (3)
Year of publication
- 2021 (3)
Document Type
- Journal article (3)
Language
- English (3)
Keywords
Institute
- Klinik und Poliklinik für Nuklearmedizin (3) (remove)
Purpose
While [18F]-fluorodeoxyglucose ([18F]FDG) is the standard for positron emission tomography/computed tomography (PET/CT) imaging of oral squamous cell carcinoma (OSCC), diagnostic specificity is hampered by uptake in inflammatory cells such as neutrophils or macrophages. Recently, molecular imaging probes targeting fibroblast activation protein α (FAP), which is overexpressed in a variety of cancer-associated fibroblasts, have become available and might constitute a feasible alternative to FDG PET/CT.
Methods
Ten consecutive, treatment-naïve patients (8 males, 2 females; mean age, 62 ± 9 years) with biopsy-proven OSCC underwent both whole-body [18F]FDG and [68Ga]FAPI-04 (FAP-directed) PET/CT for primary staging prior to tumor resection and cervical lymph node dissection. Detection of the primary tumor, as well as the presence and number of lymph node and distant metastases was analysed. Intensity of tracer accumulation was assessed by means of maximum (SUVmax) and peak (SUVpeak) standardized uptake values. Histological work-up including immunohistochemical staining for FAP served as standard of reference.
Results
[18F]FDG and FAP-directed PET/CT detected all primary tumors with a SUVmax of 25.5 ± 13.2 (FDG) and 20.5 ± 6.4 (FAP-directed) and a SUVpeak of 16.1 ± 10.3 ([18F]FDG) and 13.8 ± 3.9 (FAP-directed), respectively. Regarding cervical lymph node metastases, FAP-directed PET/CT demonstrated comparable sensitivity (81.3% vs. 87.5%; P = 0.32) and specificity (93.3% vs. 81.3%; P = 0.16) to [18F]FDG PET/CT. FAP expression on the cell surface of cancer-associated fibroblasts in both primary lesions as well as lymph nodes metastases was confirmed in all samples.
Conclusion
FAP-directed PET/CT in OSCC seems feasible. Future research to investigate its potential to improve patient staging is highly warranted.
Purpose
While [\(^{18}\)F]-fluorodeoxyglucose ([\(^{18}\)F]FDG) is the standard for positron emission tomography/computed tomography (PET/CT) imaging of oral squamous cell carcinoma (OSCC), diagnostic specificity is hampered by uptake in inflammatory cells such as neutrophils or macrophages. Recently, molecular imaging probes targeting fibroblast activation protein α (FAP), which is overexpressed in a variety of cancer-associated fibroblasts, have become available and might constitute a feasible alternative to FDG PET/CT.
Methods
Ten consecutive, treatment-naïve patients (8 males, 2 females; mean age, 62 ± 9 years) with biopsy-proven OSCC underwent both whole-body [\(^{18}\)F]FDG and [\(^{68}\)Ga]FAPI-04 (FAP-directed) PET/CT for primary staging prior to tumor resection and cervical lymph node dissection. Detection of the primary tumor, as well as the presence and number of lymph node and distant metastases was analysed. Intensity of tracer accumulation was assessed by means of maximum (SUV\(_{max}\)) and peak (SUV\(_{peak}\) standardized uptake values. Histological work-up including immunohistochemical staining for FAP served as standard of reference.
Results
[\(^{18}\)F]FDG and FAP-directed PET/CT detected all primary tumors with a SUVmax of 25.5 ± 13.2 (FDG) and 20.5 ± 6.4 (FAP-directed) and a SUVpeak of 16.1 ± 10.3 ([\(^{18}\)F]FDG) and 13.8 ± 3.9 (FAP-directed), respectively. Regarding cervical lymph node metastases, FAP-directed PET/CT demonstrated comparable sensitivity (81.3% vs. 87.5%; P = 0.32) and specificity (93.3% vs. 81.3%; P = 0.16) to [\(^{18}\)F]FDG PET/CT. FAP expression on the cell surface of cancer-associated fibroblasts in both primary lesions as well as lymph nodes metastases was confirmed in all samples.
Conclusion
FAP-directed PET/CT in OSCC seems feasible. Future research to investigate its potential to improve patient staging is highly warranted.
Purpose
In cancer of unknown primary (CUP), positron emission tomography/computed tomography (PET/CT) with the glucose analog [\(^{18}\)F]FDG represents the standard imaging approach for localization of the malignant primary. Frequently, however, [\(^{18}\)F]FDG PET/CT cannot precisely distinguish between small occult tumors and chronic inflammation, especially in Waldeyer’s tonsillar ring. To improve the accuracy for detecting primary tumors in the Waldeyer’s tonsillar ring, the novel PET tracer [\(^{68}\)Ga]Ga-FAPI-4 for specific imaging of fibroblast activation protein (FAP) expression was used as a more specific target for cancer imaging.
Methods
Eight patients with suspicion of a malignant tumor in Waldeyer’s tonsillar ring or a CUP syndrome were examined. PET/CT scans with [\(^{18}\)F]-FDG and [\(^{68}\)Ga]Ga-FAPI-4 were performed for pre-operative tumor localization. After surgical resection, histopathological and immunohistochemical results were compared to PET/CT findings.
Results
Histopathology revealed a palatine or lingual tonsil carcinoma in all patients. In case of lymph node metastases smaller than 7 mm in size, the [\(^{18}\)F]FDG PET/CT detection rate of cervical lymph node metastases was higher than that of [\(^{68}\)Ga]FAPI PET/CT, while both tracers identified the primary tumors in all eight cases. The size of the primary and the lymph node metastases was directly correlated to the respective FAP expression, as detected by immunohistochemistry. The mean SUVmax for the primary tumors was 21.29 ± 7.97 for \(^{18}\)F-FDG and 16.06 ± 6.29 for \(^{68}\)Ga-FAPI, respectively (p = 0.2). The mean SUVmax for the healthy contralateral tonsils was 8.38 ± 2.45 for [\(^{18}\)F]FDG and 3.55 ± 0.47 for [\(^{68}\)Ga]FAPI (p < 0.001). The SUVmax ratio of [68Ga]FAPI was significantly different from [\(^{18}\)F] FDG (p = 0.03). Mean TBRmax for the [\(^{68}\)Ga]Ga-FAPI-4 tracer was markedly higher in comparison to [\(^{18}\)F]FDG (10.90 vs. 4.11).
Conclusion
Non-invasive imaging of FAP expression by [\(^{68}\)Ga]FAPI PET/CT resulted in a better visual detection of the malignant primary in CUP, as compared to [\(^{18}\)F]FDG imaging. However, the detection rate of lymph node metastases was inferior, presumably due to low FAP expression in small metastases. Nevertheless, by offering a detection method for primary tumors with the potential of lower false positive rates and thus avoiding biopsies, patients with CUP syndrome may benefit from [\(^{68}\)Ga]FAPI PET/CT imaging.