Metabolic Tumor Volume And Total Lesion Glycolysis On Fdg-Pet/Ct Are Possible Prognostic Factors For Stage I Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

The aim of this study was to determine whether metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are associated with outcomes in stage I lung cancer patients treated with stereotactic body radiation therapy (SBRT). A total of 47 patients with 48 lesions (37 males, 10 females) with stage I lung cancer underwent FDG-PET/CT before SBRT at our institution between January 2001 and December 2011. Nineteen lesions were adenocarcinomas, 12 lesions were squamous cell carcinomas, 2 lesions were non-small cell carcinomas and 15 lesions were pathologically unclear. MTVmax, MTV2, MTV4, MTV6, TLG40%, TLG50% and TLG60% were calculated. Prognostic factors for overall survival (OS) and local control (LC) were analyzed using Cox’s proportional hazards regression model, and survival curves were calculated using the Kaplan-Meier method. Receiver operating characteristics curves (ROC curves) of PET parameters for OS and LC were calculated. The values of area under the curve (AUC) of PET parameters were compared by using the X2 test. The median follow-up period for survivors was 36.9 months. Three-year OS and LC rates were 57.3% and 75.9%, respectively, and 5-year OS and LC rates were 32.7% and 63.5%, respectively. Nine patients had local recurrence and 11 patients had distant organ metastases. Eleven patients died of the primary disease and 13 patients died of other causes. In univariate analyses, gender (p=0.046), tumor size (p=0.017), MTV２ (p=0.019), MTV４ (p=0.028), TLG40% (p=0.037), TLG50% (p=0.038) and TLG60% (p=0.046) were significant predictors for OS. Tumor size (P<0.001), MTV２ (p<0.001), MTV４ (p=0.005), MTV6 (p=0.029), TLG40% (p<0.001), TLG50% (p=0.002) and TLG60% (p=0.004) were significant predictors for LC. SUVmax was not a significant predictor for OS or LC. The log-rank test showed that lower SUVmax (p=0.0443), MTV2 (p=0.0081) and MTV4 (p=0.0345) were associated with significantly better OS and that lower TLG40% (p=0.0396) was associated with significantly better LC. The largest AUC for OS was MTV2, and the largest AUC for LC was TLG40%. The AUC for LC of TLG40% was significantly different from the AUC for SUVmax (p=0.0461). Our results suggested that tumor size, MTV and TLG are prognostic factors in patients with stage I lung cancer treated by SBRT. MTV and TLG are better prognostic factors than SUVmax for OS and LC.