Diagnostic Value of Dynamic F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (F-FDG PET-CT) in Cervical Lymph Node Metastasis of Nasopharyngeal Cancer.

BACKGROUND AND PURPOSE

Dynamic F-FDG PET-CT scanning can accurately quantify F-FDG uptake and has been successfully applied in diagnosing and evaluating therapeutic effects in various malignant tumors. There is no conclusion as to whether it can accurately distinguish benign and malignant lymph nodes in nasopharyngeal cancer. The main purpose of this study is to reveal the diagnostic value of dynamic PET-CT in cervical lymph node metastasis of nasopharyngeal cancer through analysis.

METHOD

We first searched for cervical lymph nodes interested in static PET-CT, measured their SUV-Max values, and found the corresponding lymph nodes in magnetic resonance images before and after treatment. The valid or invalid groups were included according to the changes in lymph node size before and after treatment. If the change in the product of the maximum diameter and maximum vertical transverse diameter of the lymph node before and after treatment was greater than or equal to 50%, they would be included in the valid group. If the change was less than 50%, they would be included in the invalid group. Their K values were measured on dynamic PET-CT and compared under different conditions. Then, we conducted a correlation analysis between various factors and K values. Finally, diagnostic tests were conducted to compare the sensitivity and specificity of K and SUV-Max.

RESULT

We included 67 cervical lymph nodes from different regions of 51 nasopharyngeal cancer patients and divided them into valid and invalid groups based on changes before treatment. The valid group included 50 lymph nodes, while the invalid group included 17. There wer significant differences ( < 0.001) between the valid and the invalid groups in SUV-Max, K-Mean, and K-Max values. When the SUV-Max was ≤4.5, there was no significant difference in the K-Mean and K-Max between the two groups ( > 0.05). When the SUV-Max was ≤4.5 and pre-treatment lymph nodes were <1.0 cm, the valid group had significantly higher K-Mean (0.00910) and K-Maximum (0.01004) values than the invalid group (K-Mean = 0.00716, K-Max = 0.00767) ( < 0.05). When the SUV-Max was ≤4.5, the pre-treatment lymph nodes < 1.0 cm, and the EBV DNA replication normal, K-Mean (0.01060) and K-Max (0.01149) in the valid group were still significantly higher than the invalid group (K-Mean = 0.00670, K-Max = 0.00719) ( < 0.05). The correlation analysis between different factors (SUV-Max, T-stage, normal EB virus DNA replication, age, and pre-treatment lymph node < 1.0 cm) and the K value showed that SUV-Max and a pre-treatment lymph node < 1.0 cm were related to K-Mean and K-Max. Diagnostic testing was conducted; the AUC value of the SUV-Max value was 0.8259 (95% confidence interval: 0.7296-0.9222), the AUC value of the K-Mean was 0.8759 (95% confidence interval: 0.7950-0.9567), and the AUC value of the K-Max was 0.8859 (95% confidence interval: 0.8089-0.9629). After comparison, it was found that there was no significant difference in AUC values between K-Mean and SUV-Max ( = 0.220 > 0.05), and there was also no significant difference in AUC values between K max and SUV-Max ( = 0.159 > 0.05). By calculating the Youden index, we identified the optimal cut-off value. It was found that the sensitivity of SUV-Max was 100% and the specificity was 66%, the sensitivity of K-Mean was 100% and the specificity was 70%, and the sensitivity of K-Max was 100% and the specificity was 72%. After Chi-Square analysis, it was found that there was no significant difference in specificity between K-Mean and SUV-Max ( = 0.712), and there was also no significant difference in specificity between K-Max and SUV-Max ( = 0.755).

CONCLUSION

Dynamic PET-CT has shown a significant diagnostic value in diagnosing cervical lymph node metastasis of nasopharyngeal cancer, especially for the small SUV value, and lymph nodes do not meet the metastasis criteria before treatment, and EBV DNA replication is normal. Although the diagnostic accuracy, sensitivity, and specificity of dynamic PET-CT were not significantly different from traditional static PET-CT, the dynamic PET-CT had a more accurate tendency.