2.3. Statistical Analysis
PD, death, primary lung tumor
REGRESSION, DISEASE PROGRESSION, DISEASE
The primary endpoint for this study was progressive disease (PD). The explanatory variables were baseline characteristics, including the primary lung tumor size and “number of involved organs”, from the CT and patient’s age, sex, smoking status and pack years, and ECOG.To illustrate the relationship between PD and the baseline characteristics, we first compared the baseline characteristics between two response groups (PD vs. DC) using the Kruskal–Wallis test for continuous, and chi-square or Fisher’s exact test for categorical, variables.Then, the associations between the baseline characteristics and PD were examined using uni- and multivariate (MV) logistic regression analyses. To restrict the number of variables in the MV analysis, we considered only the variables that showed a trend of significant associationd with PD (Then, individual patient’s “risk of progression” was calculated using the best MV logistic model (patients were excluded from the MV model if there were missing data in any of the explanatory variables). Patients were separated into the “low-” or “high-risk of progression” group by comparing their calculated risk to the Youden or topleft cut-off (i.e., high- vs. low-risk was defined if the calculated risk was higher or lower than the Youden or topleft cut-off).The progression-free survival (PFS) and overall survival (OS) between the predicted high- vs. low-risk progression groups were compared by Kaplan–Meier plots using log-rank tests. PFS was defined as the time from starting pembrolizumab to the earliest CT date that showed disease progression or the latest available CT date for patients with no sign of progression. OS was defined as the time from starting pembrolizumab to death or the date of the last follow-up.All statistical analyses were performed with R software (Version 4.1.3. 2022-03-10. R: The R Project for Statistical Computing (r-project.org). All statistical tests were two-sided and considered significant with a 