Dual-Time Point 68 Ga-FAPI-04 PET/CT Improves Tumor Delineation and Cervical Lymph Node Metastasis Identification in Patients With Head and Neck Squamous Cell Carcinoma.

PURPOSE

The purpose of this study was to evaluate the benefit of dual-time point 68 Ga-FAPI-04 PET/CT in staging head and neck squamous cell carcinoma (HNSCC).

PATIENTS AND METHODS

Sixty-nine treatment-naive patients with HNSCC were enrolled. Each patient underwent whole-body 68 Ga-FAPI-04 PET/CT at approximately 30 minutes postinjection and a delayed scan in head and neck region at 2 hours. Radiotracer uptake (SUV max ), tumor-to-background ratio, change in SUV max (∆SUV max ), retention index, diagnostic performance, and staging were explored. Histopathology was the reference standard.

RESULTS

Primary tumors showed similar average SUV max between early (17.89) and delayed scans (17.86, P = 0.241). However, the tumor-to-background ratios of delayed imaging were all significantly higher than those of early imaging (all P < 0.001). In 38 patients who underwent neck dissection, metastatic lymph nodes showed higher mean SUV max on delayed imaging than on early imaging (early 10.53 ± 5.98 vs delayed 11.71 ± 6.36, P < 0.001), whereas nonmetastatic lymph nodes showed the opposite result (early 3.51 ± 0.51 vs delayed 2.58 ± 0.63, P = 0.002). The mean ∆SUV max and retention index of metastatic and nonmetastatic lymph nodes were 1.19 versus -0.93 and 12.79% versus -26.55%, respectively. N staging was correctly altered in 3 (3/38) patients based on delayed images.

CONCLUSIONS

Delayed 68 Ga-FAPI-04 PET/CT can effectively acquire high-contrast images, better tumor delineation, and detect hidden lesions near or within the tissues influenced by physiological uptake for HNSCC. In addition, dual-time point imaging adds diagnostic value for the differentiation of metastatic from nonmetastatic lymph nodes.