Comparison Of Metabolic Volume Parameters Calculated By Different Thresholds Of ¹⁸F-FDG PET/CT In The Prognostic Evaluation Value Of Non-small Cell Lung Cancer

Objective:To evaluate the metabolic volume parameters calculated by different SUV thresholds of ¹⁸F FDG PET/CT in the prognosis of NSCLC.Methods:178 non-small cell lung cancer patients who received ¹⁸F FDG PET/CT examination in nuclear medicine department of the First Affiliated Hospital of Chongqing Medical University from January 2017 to December 2018 were collected.Different thresholds were determined by standardized uptake value（SUV）=2.5,SUV=4.0,40%the maximum SUV（SUVmax）and 50%SUVmax,respectively.The the mean SUV（SUVmean）,metabolic tumor volume（MTV）and total lesion glycolysis（TLG）of each method were calculated according to the delineated area of interest（ROI）system.The success rate of the four methods was compared by chi square test.The correlation and consistence among the metabolic volume parameters obtained by four methods were evaluated by Pearson coefficient.The prediction ability of metabolic volume parameters to survival state was evaluated by ROC curve,and the best survival cutoff value was obtained.The Kaplan Meier survival curve was drawn after grouping the best truncation values,and the difference of the curves was tested by log rank.Results:Four different thresholds were used to segment the ROI automatically in 178 patients with non-small cell lung cancer（NSCLC）.With 40%SUVmax as the threshold,163 patients were successfully segmented,and the success rate was highest,91.6%.With the threshold of SUV=2.5,the success rate was lowest,71.2%.According to the survival status of patients,MTV2.5,TLG2.5,MTV4.0,TLG4.0,MTV40%,TLG40%,MTV50 and TLG50 in the progressive group were higher than those in the non-progressive group,and the differences between the two groups were statistically significant.ROC curve was used to analyze the effect of metabolic parameters on the survival status of patients with non-small cell lung cancer.The results showed that metabolic volume parameters had important value for prognosis evaluation of non-small cell lung cancer.All the parameters of volume metabolism have good predictive power of survival state,and the best diagnostic efficiency is MTV2.5.However,there is no significant difference between the parameters of volume metabolism obtained by different methods in predicting survival state.According to the best cutoff value,the volume parameters obtained by four different thresholds were divided into high metabolic parameters group and low metabolic parameters group,and then Kaplan-Meier survival analysis was performed.Kaplan-Meier survival analysis showed that there were significant differences in the two groups（P<0.001）,and the median survival time of the high metabolic parameter group was significantly shorter than that of the low metabolic parameter group.Conclusion:All the volume metabolism parameters obtained by the four different threshold segmentation methods have good survival state prediction performance,and can be used for the prognosis analysis of non-small cell lung cancer.40%SUVmax is the threshold with the highest success rate,which is worthy of promotion.