Correlative analysis
tumor
TUMOR
Correlative analysis to explore potential biomarkers, included PD-L1 expression and paired-exome sequencing of blood and tumor ctDNA.The PD-L1 status was immunohistochemically examined by the DAKO PD-L1 (28-8 pharmDx) assay. ctDNA was analyzed using a tumor-informed ctDNA panel for targeted gene sequencing. Briefly, patients with tumor tissues available were sequenced at first for specific tumor variants identification. Two distinct methods were employed to call plasma ctDNA variants depending on if they were identified in matched tumor tissues. The detailed description of plasma ctDNA analysis is available in the Plasma samples collection was carried out at pre-treatment (T0), prior to the third cycle of neoadjuvant treatment (T1), after neoadjuvant treatment prior to surgery (T2), and within one month after surgery (T3, prior to adjuvant treatment). ctDNA clearance was defined as a pre-surgery alteration from detectable ctDNA at T0 to undetectable ctDNA at T2.