The Diagnostic And Prognostic Value Of ¹⁸F-FDG PET/CT In Patients With Small Cell Lung Cancer

Objective:To compare the morphological and metabolic characteristics of¹⁸F-fluorodeoxyglucose-positron emission tomography(¹⁸F-PET/CT)between central small cell lung cancer?SCLC?and central squamous cell carcinoma?SCC?and to investigate the prognostic value of ¹⁸F-PET/CT in untreated patients with limited-stage small cell lung cancer?LS-SCLC?.Methods:Part one:Seventy-eight patients with pathologically proved central SCLC and one hundred and twenty-six patients with pathologically proved central SCC from October 2010 to December 2017 were retrospectively collected.The clinical information?including age,gender,smoking status?,CT morphological characteristics?including lesion location,lesion size,morphology,density,relationships between macroaxis of the tumor and bronchus courser,changes of involved bronchial lumen,obstructive signs,changes of lymph node,invasion of mediastinal vessels,pleural effusion,distant metastasis?and maximum standardized uptake value(SUV_max).The differences in age,lesion size and SUVmax were compared by using independent sample t test,and the gender,smoking status,lesion location,morphology,density,relationships between macroaxis of the tumor and bronchus courser,changes of involved bronchial lumen,obstructive signs,changes of lymph node,invasion of mediastinal vessels,pleural effusion and distant metastasis were compared using?² test.The parameters aboved with statistically significant differences were performed by no-conditional logistic regression analysis.The receiver operating characteristic?ROC?curve was performed to calculate the area under the curve of the SUVmax single parameter and ¹⁸F-PET/CT in the differential diagnosis of central SCLC and SCC and to obtain the optimal cut-off point and its corresponding sensitivity and specificity.Part two:Fifty-two patients with LS-SCLC who underwent baseline ¹⁸F-PET/CT scan from October 2010 to December2017 were reviewed.The clinical information of patients and maximum standardized uptake value?SUVmax?,mean standardized uptake value?SUVmean?,metabolic tumor volume?MTV?,total lesion glycolysis?TLG?of all lesions were recorded,including SUVmax of primary tumor?PtSUVmx?,SUVmean of primary tumor?PtSUVmean?,MTV of primary tumor?PtMTV?,TLG of primary tumor?PtTLG?,SUVmax of metastatic lymph node?LnSUVmx?,MTV of metastatic lymph node?LnMTV?,TLG of metastatic lymph node?LnTLG?,the sum of MTV?SumMTV?and the sum of TLG?SumTLG?.The above parameters were compared by using the Mann-Whitney U test.The receiver operating characteristic?ROC?curves were ploted to estimate the optimal cut-off point and the sensitivity and specificity corresponding to the critical value were obtained.The Kaplan-Meier method and log-rank test was performed for survival analysis.The test level for?49?<0.05Results:Part one:We enrolled seventy-eight patients with central SCLC,including68 cases of male and 10 cases of female,whose mean age was?62.0±9.0?year,and one hundred and twenty-six patients with central SCC,including 113 cases of male and 10cases of female,whose mean age was?64.2±8.5?year.The SUVmax?13.18±5.19?in the central SCC group was higher than that in the SCLC group?10.39±4.28?,and the difference was statistically significant??49?<0.05?.In the central SCLC group,the irregular tumor body,conformity between the macroaxis of the tumor and the bronchus courser,lymph node fusion,bronchostenosis without blocking,bronchial obstruction,invasion of mediastinal vessels,pleural effusion and distant metastasis were 60?60/78?,32?32/78?,40?40/78?,14?14/78?,32?32/78?,16?16/78?,23?23/78?,32?32/78?respectively.And in the SCC group,they were 77?77/126?,34?34/126?,12?12/126?,5?5/126?,83?83/126?,3?3/126?,14?14/126?,14?14/126?respectively.The difference between central SCLC and SCC was statistically significant??49?<0.05?.Invasion of mediastinal vessels and SUVmax were independent factors of differenting SCLC and SCC,and the OR values were 19.255,0.890 respectively.The area under the curve?AUC?of SUVmax was 0.650,and when SUVmax=13.90,the sensitivity,specificity were 84.6%,50.0%respectively.The AUC of¹⁸F-PET/CT in the differentiaing diagnosis was 0.914,the sensitivity and specificity were88.5%,81.7%.Part two:Fity-two patients with LS-SCLC were include,whose median followed-up time was 20?range:6-84?months.At the end of follow-up,6 patients were lost,27 died,25 survived and 24 relapsed.For patients with LS-SCLC,there were statistically significant differences in LnSUVmax,LnMTV,LnTLG,SumMTV,and SumTLG between the progression and non-progression group??49?<0.05?.The LnSUVmax,LnMTV,LnTLG,SumMTV and SumTLG optimal cut-off points were 8.20,10.66,57640.10,64.07,296504.80,respectively,and the corresponding sensity and specificity87.5%and 63.6%,79.2%and 68.2%,75.0%and 72.7%,70.8%and 77.3%,66.7%and72.7%.The AUC were 0.756,0.773,0.761,0.735,0.699,respectively.Inter-group survival analysis showed that LnSUVmax,LnMTV,LnTLG,SumMTV,and SumTLG were the influencing factors of PFS in patients with LS-SCLC??49?<0.05?,while LnMTV was the influencing factor of OS??49?<0.05?.Conclusion:The invasion of mediastinal vessels and SUVmax are independent factors influencing central SCLC and central SCC.Central SCLC is more likely to have invasion of mediastinal vessels,while central SCC has higher SUVmax.The morphological and metabolic characteristics based on ¹⁸F-FDG PET/CT are significantly different,and play a great role in the differential diagnosis of central SCLC and SCC.The metabolic parameters of ¹⁸F-FDG PET/CT before treatment,such as LnSUVmax,LnMTV,LnTLG,SumMTV,SumTLG,are meaningful for predicting tumor progression,among which LnSUVmax,LnTLG,SumMTV,SumTLG are the influencing factors of PFS in LS-SCLC patients,LnMTV It is the influencing factor of PFS and OS.