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

Background This study aimed to compare the diagnostic value of [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F]FDG PET/CT imaging for primary lesions and metastatic lymph nodes in patients with tonsil cancer. Method Twenty-one tonsil cancer patients who underwent [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F]FDG 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 Ga]Ga-DOTA-FAPI-04 PET/CT (20/22) than for [ 18 F]FDG PET/CT (9/22). Although [ 68 Ga]Ga-DOTA-FAPI-04 uptake (SUVmax, 5.03 ± 4.06) was lower than [ 18 F]FDG uptake (SUVmax, 7.90 ± 4.84, P = 0.006), [ 68 Ga]Ga-DOTA-FAPI-04 improved the distinction between the primary tumor and contralateral normal tonsillar tissue. The TBR was significantly higher for [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT (3.19 ± 2.06) than for [ 18 F]FDG PET/CT (1.89 ± 1.80) (p < 0.001). In lymph node analysis, SUVmax and TBR were not significantly different between [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F]FDG 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 Ga]Ga-DOTA-FAPI-04 PET/CT were higher than those of [ 18 F]FDG PET/CT in diagnosing metastatic cervical lymph nodes (all P < 0.05). Conclusion The availability of [ 68 Ga]Ga-DOTA-FAPI-04 complements the diagnostic results of [ 18 F]FDG by improving the detection rate of primary lesions and the diagnostic accuracy of cervical metastatic lymph nodes in tonsil cancer compared to [ 18 F]FDG.