Prospective study of ^99mTc-3PRGD₂ SPECT/CT diagnosing metastatic lymph nodes in esophageal squamous cell carcinoma

Lymph node (LN) metastasis is a significant prognostic factor for esophageal squamous cell carcinoma (ESCC), and there are no satisfactory methods for accurately predicting metastatic LNs. The present study aimed to assess the efficacy of ^99mTc-3PRGD₂ single-photon emission computed tomography (SPECT)/computed tomography (CT) for diagnosing metastatic LNs in ESCC.

A total of 15 enrolled patients with ESCC underwent ^99mTc-3PRGD₂ SPECT/CT and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) examinations preoperatively. High-definition bone carving reconstruction technology (HD-xSPECT Bone) was applied to quantitatively assess the LN's SUV_max via SPECT/CT. The two methods were compared for diagnosing metastatic LNs with pathology as the gold standard.

Among 15 patients, 23 metastatic lymph node stations (mLNSs) were predicted by SPECT/CT, with a mean SUV_max of 2.71 ± 1.34, of which 15 were pathologically confirmed; 32 mLNSs were predicted by PET/CT with a mean SUV_max of 4.41 ± 4.02, of which 17 were pathologically confirmed. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of SPECT/CT for diagnosing metastatic LNs were 62.50%, 91.30%, 85.34%, 65.22%, and 90.32%, respectively, and those of PET/CT were 70.83%, 83.70%, 81.03%, 53.13%, and 91.67%, respectively. There was no significant difference in sensitivity (p = 0.061) or specificity (p = 0.058) between the two methods. The AUC_SPECT/CT was 0.816 and the SUV_max threshold was 2.5.

^99mTc-3PRGD₂ SPECT/CT might be an effective method for diagnosing metastatic LNs in ESCC, especially in combination with HD-xSPECT Bone. The diagnostic efficiency of this method was noninferior to that of ¹⁸F-FDG PET/CT. The SUV_max threshold of 2.5 showed the highest agreement with the pathology findings.