Head-to-head comparison of 68GaGa-DOTA-FAPI-04 and 18FFDG PET/CT for the evaluation of tonsil cancer and lymph node metastases: a single-centre retrospective study

Abstract Background This study aimed to compare the diagnostic value of 68 GaGa-DOTA-FAPI-04 and 18 FFDG PET/CT imaging for primary lesions and metastatic lymph nodes in patients with tonsil cancer. Method Twenty-one tonsil cancer patients who underwent 68 GaGa-DOTA-FAPI-04 and 18 FFDG PET/CT scans within two weeks in our centre were retrospectively enrolled. The maximum standardized uptake value (SUVmax) and tumor-to-background ratio (TBR) of the two tracers were compared by using the Mann‒Whitney U test. In addition, the sensitivity, specificity, and accuracy of the two methods for diagnosing metastatic lymph nodes were analysed. Results In detecting primary lesions, the efficiency was higher for 68 GaGa-DOTA-FAPI-04 PET/CT (20/22) than for 18 FFDG PET/CT (9/22). Although 68 GaGa-DOTA-FAPI-04 uptake (SUVmax, 5.03 ± 4.06) was lower than 18 FFDG uptake (SUVmax, 7.90 ± 4.84, P = 0.006), 68 GaGa-DOTA-FAPI-04 improved the distinction between the primary tumor and contralateral normal tonsillar tissue. The TBR was significantly higher for 68 GaGa-DOTA-FAPI-04 PET/CT (3.19 ± 2.06) than for 18 FFDG PET/CT (1.89 ± 1.80) (p < 0.001). In lymph node analysis, SUVmax and TBR were not significantly different between 68 GaGa-DOTA-FAPI-04 and 18 FFDG PET/CT (7.67 ± 5.88 vs. 8.36 ± 6.15, P = 0.498 and 5.56 ± 4.02 vs. 4.26 ± 3.16, P = 0.123, respectively). The specificity and accuracy of 68 GaGa-DOTA-FAPI-04 PET/CT were higher than those of 18 FFDG PET/CT in diagnosing metastatic cervical lymph nodes (all P < 0.05). Conclusion The availability of 68 GaGa-DOTA-FAPI-04 complements the diagnostic results of 18 FFDG by improving the detection rate of primary lesions and the diagnostic accuracy of cervical metastatic lymph nodes in tonsil cancer compared to 18 FFDG.