Metabolic tumor volume on FDG-PET/CT is a possible prognostic factor for Stage I lung cancer patients treated with stereotactic body radiation therapy: a retrospective clinical study

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). Thirty-eight patients underwent [F-18] fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG-PET/CT) within 60 days before SBRT at our institution between January 2001 and December 2011. The maximum standardized uptake value (SUVmax), MTV2, MTV4, MTV6, TLG(40%), TLG(50%) and TLG(60%) were calculated. Prognostic factors for overall survival (OS) and local control (LC) were analyzed using Cox's proportional hazards model, and survival curves were calculated using the Kaplan-Meier method. Receiver operating characteristics (ROC) curves of PET parameters for OS and LC were calculated. The median follow-up period for survivors was 37.7 months. Three-year OS and LC rates were 56.4% and 70.5%, respectively, and 5-year OS and LC rates were 36.8% and 70.5%, respectively. In univariate analyses, tumor diameter (P = 0.019), single dose >= 10 Gy (P = 0.017), MTV2 (P = 0.030) and MTV4 (P = 0.048) were significant predictors for OS. Tumor diameter (P < 0.001), single dose = 10 Gy (P = 0.007), SUVmax (P = 0.035), MTV2 (P < 0.001), MTV4 (P = 0.003), MTV6 (P = 0.017), TLG(40%) (P < 0.001), TLG(50%) (P = 0.001) and TLG(60%) (P = 0.003) were significant predictors for LC. SUVmax was not a significant predictor for OS. We made the ROC curves at PET parameters, and the largest area under the curve value for OS was MTV2 and for LC was TLG(40%). Tumor diameter, single dose >= 10 Gy, MTV2 and MTV4 are prognostic factors for OS and LC rates and MTV2 is a better prognostic factor for OS than other PET parameters.