Metabolic active tumour volume quantified on [18F]FDG PET/CT further stratifies TNM stage IV non-small cell lung cancer patients

Purpose This study aimed to assess whether the whole body metabolic active tumour volume (MTVWB), quantified on staging [F-18]FDG PET/CT, could further stratify stage IV non-small cell lung cancer (NSCLC) patients. Methods A group of 160 stage IV NSCLC patients, submitted to staging [F-18]FDG PET/CT between July 2010 and May 2020, were retrospectively evaluated. MTVWB was quantified. Univariate and multivariate Cox regressions were carried out to assess correlation with overall survival (OS). C-statistic was used to test predictive power. Kaplan-Meier survival curves with Log-Rank tests were performed to compute statistical differences between strata from dichotomized variables and to calculate the estimated mean survival times (EMST). Survival rates at 1 and 5 years were calculated. Results MTVWB was a statistically significant predictor of OS on univariate (p < 0.0001) and multivariate analyses (p < 0.0001). The multivariate model with MTVWB (Cindex +/- SE = 0.657 +/- 0.024) worked significantly better as an OS predictor than the cTNM model (Cindex +/- SE = 0.544 +/- 0.028) (p = 0.003). An EMST of 29.207 +/- 3.627(95% CI 22.099-36.316) months and an EMST of 10.904 +/- 1.171(95% CI 8.609-13.199) months (Log-Rank p < 0.0001) were determined for patients with MTVWB < 104.3 and MTVWB >= 104.3, respectively. In subsamples of stage IVA (cut-off point = 114.5) and IVB patients (cut-off point = 191.1), statistically significant differences between EMST were also reported, with p-values of 0.0001 and 0.0002, respectively. In both substages and in the entire cohort, patients with MTVWB >= cut-off points had lower EMST and survival rates. Conclusion Baseline MTVWB, measured on staging [F-18]FDG PET/CT, further stratifies stage IV NSCLC patients. This parameter is an independent predictor of OS and provides valuable prognostic information over the 8th edition of cTNM staging.