Validating A Pet/Ct Volumetric Prognostic Index For Non-Small Cell Lung Cancer.

8516 Background: We previously developed a PET/CT volumetric prognostic staging system (PVP index) using Cox regression models to predict the hazard of death using both whole-body metabolic tumor volume (MTVWB ) and TNM staging, which has greater prognostic power than TNM stage or MTVWB alone in non-small cell lung cancer (NSCLC). This study is to validate its prognostic accuracy in a different NSCLC population. Methods: We performed an IRB-approved retrospective review of 667 patients with a new NSCLC diagnosis and with FDG PET/CT scans obtained with a number of different scanners (302 patients with a Siemens Reveal HD scanner, 133 with a Siemens mCT scanner and 232 with outside hospital scanners) from 2004 to 2015. Clinical TNM stage, initial PET MTVWB , and long-term survival data were collected. The PVP index was calculated for each patient based on their MTVWB and TNM stage using our published formula: 0.360*ln(MTVWB ) + 0.424*I(TNM = III) + 0.890*I(TNM = IV), with the indicator function I(·) yielding a value of 1 when its argument is true and 0 otherwise. Kaplan-Meier survival analysis, the log-rank test and univariate Cox regression analysis with Gonen and Heller's Concordance Index (GHCI) were used. Results: Their median age was 68 years, with 55% women and median follow-up among 289 survivors of 39 months. Clinical TNM stages were I (30%), II (11%), III (30%), and IV (29%). Tumor histology was adenocarcinoma (54%), squamous carcinoma (28%) and other types (18%). 38% of patients had surgery, 59% had chemotherapy, and 40% had radiation. PVP was inversely associated with overall survival (OS) (p < 0.001). Five year OS rates of patients in the 1st, 2nd, 3rd and 4th PVP index groups were 58%, 30%,18%, and 12%, respectively. Univariate Cox regression analysis showed significant association of the PVP index with OS (HR = 2.07, 95% CI = 1.84-2.32, p < 0.001). The PVP index yielded greater discriminatory power (GHCI = 0.68) than those of TNM stage (GHCI = 0.66, p < 0.001). Conclusions: This study used a large validation cohort of NSCLC patients, imaged on a number of PET/CT systems, to confirm that the PVP index has good discriminatory ability and greater prognostic value than TNM stage alone.