Change from baseline in biomarkers of interest
tumor, tumors
TUMOR, TUMORS
Changes in biomarkers at baseline, cycle 2, and surgery were assessed. These findings are exploratory, as the number of samples available post-baseline was limited and patients who did not achieve pCR were more likely to have biomarker results at cycle 2 (71.5% of tissue availability for non-pCR subgroup vs. 28.5% for pCR subgroup). PAM50 intrinsic tumor subtype, PD-L1-positive IHC status, percentage of stromal TILs, and HER2 gene expression levels (Nanostring) were analyzed by the treatment arm at different time points. HER2-E tumors were the most prevalent PAM50 subtype in both treatment arms at baseline (Additional file PD-L1-positive IHC status was observed in similar percentages of patients at baseline (41.5%) and cycle 2 (37.3%) in the TCH + P arm, decreasing to 21.4% at surgery. In the T-DM1 + P arm, in contrast, PD-L1 positivity increased from 45.9% at baseline to 53.8% at cycle 2 and 72.5% at surgery (Additional file 