RT Journal Article
SR Electronic
T1 The Added Value of <sup>68</sup>Ga-FAPI PET/CT in Patients with Head and Neck Cancer of Unknown Primary with <sup>18</sup>F-FDG–Negative Findings
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 875
OP 881
DO 10.2967/jnumed.121.262790
VO 63
IS 6
A1 Bingxin Gu
A1 Xiaoping Xu
A1 Ji Zhang
A1 Xiaomin Ou
A1 Zuguang Xia
A1 Qing Guan
A1 Silong Hu
A1 Zhongyi Yang
A1 Shaoli Song
YR 2022
UL http://jnm.snmjournals.org/content/63/6/875.abstract
AB 18F-FDG PET/CT plays an important role in locating the primary tumor for patients with head and neck cancer of unknown primary (HNCUP). Nevertheless, in some cases it can be challenging to locate the primary malignancy on 18F-FDG PET/CT scans. Because 68Ga-radiolabeled fibroblast activation protein inhibitor (FAPI) PET/CT has promising results in detecting different tumor entities, our study aimed to evaluate the performance of 68Ga-FAPI PET/CT for detecting the primary tumor in HNCUP patients with negative 18F-FDG findings. Methods: Eighteen patients (16 men and 2 women; median age, 55 y; age range, 24–72 y) with negative 18F-FDG findings were enrolled in this study. All patients underwent 18F-FDG and 68Ga-FAPI PET/CT within 1 wk. Biopsy and histopathologic examinations were performed in the sites with positive 68Ga-FAPI PET/CT findings. Results: 68Ga-FAPI PET/CT detected the primary tumor in 7 of 18 patients (38.89%). Among these 7 patients, primary tumor sites included the nasopharynx (n = 1), palatine tonsil (n = 2), submandibular gland (n = 2), and hypopharynx (n = 2). The primary tumors showed moderate to intensive uptake of 68Ga-FAPI (mean SUVmax, 8.79; range, 2.60–16.50) and excellent tumor–to–contralateral normal-tissue ratio (mean SUVmax ratio, 4.50; range, 2.17–8.21). In lesion-based analysis, 65 lymph nodes and 17 bone metastatic lesions were identified. The mean SUVmax of lymph node metastases was 9.05 ± 5.29 for 18F-FDG and 9.08 ± 4.69 for 68Ga-FAPI (P = 0.975); the mean SUVmax of bone metastases was 8.11 ± 3.00 for 18F-FDG and 6.96 ± 5.87 for 68Ga-FAPI (P = 0.478). The mean tumor-to-background ratios of lymph node and bone metastases were 10.65 ± 6.59 versus 12.80 ± 8.11 (P = 0.100) and 9.08 ± 3.35 versus 9.14 ± 8.40 (P = 0.976), respectively. Conclusion: We present the first evidence, to our knowledge, of a diagnostic role of 68Ga-FAPI PET/CT in HNCUP. Our study demonstrated that 68Ga-FAPI PET/CT has the potential to improve the detection rate of primary tumor in HNCUP patients with negative 18F-FDG findings. Moreover, 68Ga-FAPI had a performance in assessing metastases similar to that of 18F-FDG.