TP53 and neoplasm: The PPV of TP53 ctDNA detection at T1 and T4 for the presence of residual disease post NAC (non-pCR) was 78% and 88% respectively while the negative predictive value (NPV) was only 13% and 30% respectively (Table 3A), a result inferior to the ones observed when WES was used to identify private variants for each tumor.