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 [¹⁸F] fluorodeoxyglucose positron emission tomography/ computed tomography (¹⁸F-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.