Comparison of 68Ga-DOTATATE and 18F-FDG PET/CT for tumor staging and primary tumor volume delineation in patients with nasopharyngeal carcinoma.

This study evaluated the clinical utility of 68Ga-DOTATATE PET/CT compared to 18F-FDG PET/CT for tumor staging and the delineation of primary tumor volume in patients with non-keratinizing nasopharyngeal carcinoma (NPC). Forty-two individuals with pathologically confirmed non-keratinizing NPC were recruited. This study compared the detection rates of primary and metastatic tumors and the accuracy of tumor staging using two PET/CT modalities. Tumor volumes defined on PET scans using the absolute SUV of 2.5 (TH2.5), 40% of the maximum SUV (TH40%), and the relative background-dependent threshold (THbgd) were analyzed in comparison to MRI results. Comparing 68Ga-DOTATATE and 18F-FDG PET/CT, identifying primary tumors (initial detection, 100% vs. 97.3%; recurrent detection, 80.0% vs. 100%) and lymph node metastases (99.0% vs. 100%) were comparable. However, 68Ga-DOTATATE PET/CT detected more skull base bone (100% vs. 96.3%) and intracranial invasion (100% vs. 54.5%) than 18F-FDG, and consequently correctly upwardly adjusted the T-staging in 7 patients. 68Ga-DOTATATE PET/CT detected an equal number of lung metastases (24/24) but more bone metastases (97.8% vs. 84.4%) compared to 18F-FDG PET/CT, yet was less effective for liver metastases (30.4% vs. 100%). Compared with 18F-FDG PET/CT, 68Ga-DOTATATE PET/CT correctly upstaged 5 subjects and downstaged 1 subject in overall staging. Tumor volumes assessed by 68Ga-DOTATATE PET compared to 18F-FDG PET using the three threshold methods demonstrated less variability and higher agreement with MRI. Among the methods, THbgd for lesion segmentation in 68Ga-DOTATATE PET demonstrated the highest confidence level and concordance with MRI (ICC 0.95). In conclusion, 68Ga-DOTATATE PET/CT is a beneficial complement to 18F-FDG PET/CT for NPC staging, with higher accuracy for primary tumor volume delineation.