treatment and methylation status determined single nucleotide primer extension technique (MSD-SNuPET). Principal component analysis was applied to show the efficiency of the elimination of ComBat. A, B, A total of 120 probe sets with DNA methylation values after background and quantile normalization in a set of 352 non-small cell lung cancer (NSCLC) and 106 normal samples. X and Y axes represent the first and second principal components (PC1 and PC2), respectively. C-I were validation of the methylation status of the five candidate markers in an independent samples. Y-axis represents absolute DNA methylation percentage from MSD- SNuPET. LINE-1 and Reference were taken as the positive and negative control for MSD- SNuPET.