Developing Post-Treatment Pet/Ct Volumetric Prognostic Index For Non-Small Cell Lung Cancer.

e21085 Background: The aim of this study is to model and validate a post-treatment PET/CT volumetric prognostic (ptPVP) index for risk assessment after definitive therapy for NSCLC. Methods: This IRB-approved retrospective cohort study included 1028 NSCLC patients diagnosed between 2004 and 2017. Variables included: pre-treatment whole-body metabolic tumor volume (MTVwb) measured on baseline FDG PET/CT, patient age, clinical TNM stage, ECOG performance status (PS), gender, tumor histology, treatment type, and survival outcomes. Patients were assigned to a modeling cohort (531 patients) for modeling ptPVP index and a clinical index with a multivariate Cox regression model. The ptPVP index was validated with a separate validation cohort (497 patients) by comparing the prognostic value of ptPVP index against its individual independent variables and the clinical index. Results: The ptPVP index generated from the modeling cohort was comprised of 5 variables including treatment type (surgery, no surgery, and no therapy), age, clinical TNM stage (stage I or II, III, and IV), PS ( 0, 1, and ≥ 2) and MTVwb. The clinical index was comprised of above 4 clinical variables without MTVwb. Univariate Cox models showed significant association of the ptPVP index with OS with Hazard ratio (HR) of 2.72 (95% CI = 2.39-3.09, p < 0.001). The C-statistic of ptPVP index (0.71) was significantly greater than that of clinical index (0.68) (p = 0.001). In the validation cohort, univariate Cox models showed significant association of the ptPVP index with OS (HR = 3.09, 95% CI = 2.64-3.61, p < 0.001). The ptPVP index showed greater prognostic power (C-statistic = 0.72) than that of the clinical index (C-statistic = 0.70, p = 0.001), treatment type (C-statistic = 0.66, p < 0.001), MTVwb (C-statistic = 0.67, p < 0.001), age (C-statistic = 0.58, p < 0.001), clinical 9-group TNM staging (C-statistic = 0.66, p < 0.001), and PS (C-statistic = 0.57, p < 0.001). Multivariate Cox regression analysis demonstrated a significant association of ptPVP index with OS (HR = 3.06, 95% CI of 2.60-3.61, p < 0.001) after adjusting gender and NSCLC histology. A better separation of Kaplan-Meier curves of patients grouped by ptPVP index than those grouped by clinical index, MTVwb, or clinical TNM stage was evident. Conclusions: The ptPVP index developed for NSCLC patients demonstrated moderately prognostic power and better prognostic ability than its individual independent variables and clinical index without MTVwb. It provides a practical quantitative risk assessment for the patient follow-up and management after initial treatment.