Prognostic Value Of Baseline ¹⁸F-FDG PET/CT Metabolic Parameters For Radiochemotherapy In Esophageal Squamous Cell Carcinoma With Metastasis

Objective:The objective of this study was to investigate the prognostic value of primary and metastatic metabolic parameters of ¹⁸F-FDG PET/CT imaging before treatment in patients with esophageal squamous cell carcinoma（ESCC）undergoing radiotherapy and chemotherapy.Methods:106 ESCC patients who received ¹⁸F-FDG PET/CT examination in our hospital from November 2013 to April 2021 were retrospectively analyzed.All patients were pathologically confirmed as esophageal squamous cell carcinoma.The following data of patients were collected and sorted out:clinical factors included age,gender,primary location,clinical stage,degree of differentiation,and treatment method;Metabolic parameters included SUVmax of primary lesion,MTV of primary lesion（MTVp）,TLG of primary lesion（TLGp）,MTV of whole body（MTVwb）,TLG of whole body（TLGwb）,and SUVmax,MTV,TLG ratio of metastatic lesion（including lymph node metastasis and distant organ metastasis）to primary lesion（R-SUVmax,R-MTV,R-TLG）.Mann-Whitney U test or Kruskal-Wallis H test were used to analyze the differences in metabolic parameters among different clinical factors.X-tile software was used to obtain the best cut-off values of metabolic parameters.Kaplan-Meier method and Log-Rank test were used for univariate analysis,and Cox proportional risk model was used for multivariate analysis,to explore prognostic factors affecting patients’progression-free survival（PFS）and overall survival（OS）,and to further stratify ESCC patients with independent risk factors.P<0.05 was considered statistically significant.Results:1.A total of 106 patients were included in the study.There were 98 males and 8females,aged 44～88 years,with an average age of（63.9±8.8）years.The median follow-up time of the study cohort was 11 months（1～63 months）.By the end of follow-up,84 patients had disease progression（79.2%）,including 76 deaths（71.7%）,median PFS of 9 months（1～63 months）,and median OS of 11 months（1-63 months）.2.The metabolic parameters of ¹⁸F-FDG PET/CT were correlated with the clinical features of ESCC.SUVmax was different among different T stages（all P<0.001）,and MTVp and TLGp were different among different T stages and clinical stages（all P<0.05）.There were differences in MTVwb at different T stages,N stages,M stages and clinical stages（all P<0.05）,and differences in TLGwb at different T stages,N stages and clinical stages（all P<0.05）.R-SUVmax was different in different T stages and clinical stages（all P<0.05）,and R-MTV and R-TLG were different in different T stages,N stages,M stages and clinical stages（all P<0.05）.3.Univariate analysis showed that T staging,MTVp,TLGp,MTVwb,TLGwb and R-TLG were correlated with the prognosis of ESCC patients receiving radiotherapy and chemotherapy（all P<0.05）.Multivariate analysis showed that T stage and R-TLG were PFS（HR=2.210,95%CI:1.307～3.737;P=0.003;HR=3.118,95%CI:1.414-6.875,P=0.005）and OS（HR=1.885,95%CI:1.072～3.317;P=0.028;HR=2.584,95%CI:1.186～5.629;P=0.017）were independent prognostic factors.Combined with T staging and R-TLG,the patients were divided into three groups:low R-TLG and T1-2 group were low-risk group（n=34）,high R-TLG or T3-4 group were medium-risk group（n=68）,and high R-TLG and T3-4 group were high-risk group（n=4）.The results showed that,there were statistically significant differences in PFS and OS among all groups（all P<0.05）.Conclusion:T stage before chemoradiotherapy and R-TLG metabolic parameter of ¹⁸F-FDG PET/CT are independent prognostic factors affecting PFS and OS in ESCC patients.The later the T stage and the higher the R-TLG value,the shorter the survival time and the worse the prognosis of ESCC patients.Risk stratification of ESCC patients can be performed according to T stage and R-TLG,and then individualized treatment can be developed to improve prognosis.