An updated and validated PET/CT volumetric prognostic index for non-small cell lung cancer

Objectives: Whole-body metabolic tumor volume (MTVWB) and TNM staging are independent prognostic factors for overall survival (OS) in non-small cell lung cancer (NSCLC). We aimed to update and validate the PET/CT volumetric prognostic index (PVP index) using the new 8th edition TNM staging system to evaluate its prognostic power versus TNM staging and MTVWB alone. Materials and Methods: This study was a retrospective analysis of 949 non-small cell lung cancer (NSCLC) patients diagnosed between 2004 and 2014. Clinical TNM stage, MTVWB, age and gender, tumor histology type at the initial staging PET/CT exam, as well as treatment history and long-term survival data were obtained. Patients were randomly assigned to modeling or validation group. Univariate and multivariate Cox regression analyses were performed to compare PVP index, TNM stage, and MTVWB in the validation group. Results: The updated PVP index included the 3 variables TNM stage, and MTVWB and age. Univariate Cox models showed significant association of PVP index with overall survival (OS) in patients with NSCLC (with Hazard ratio HR = 2.88 in the validation group, p < 0.001). The C-statistic of the PVP index (C-statistic = 0.71 in the validation group) was significantly greater than that of 8th edition TNM staging (C-statistic = 0.68, p = 0.029), MTVWB (C-statistic = 0.68, p = 0.001), and patient age (C-statistic = 0.53, p < 0.001). Multivariate Cox regression analyses demonstrated significant association of PVP index with OS (with HR = 2.80, p < 0.001) after adjusting patient's gender and tumor histology. Conclusions: The updated PVP index provides a quantitative risk assessment for NSCLC patients using 8th edition TNM staging, MTVB, and age. The index provides a simple and practical way for the care team to incorporate the independent prognostic value of both the TNM stage and MTVWB. This approach can further improve the accuracy of overall survival prognosis.