Expression data from human breast cancers pre and post chemothrapy

Neoadjuvant chemotherapy has been shown to be equivalent to post-operative treatment for breast cancer, and allows for assessment of chemotherapy response. In a pilot trial of docetaxel (T) and capecitabine (X) neoadjuvant chemotherapy for Stage II/III BC, we assessed correlation between baseline gene expression and tumor response to treatment, and examined changes in gene expression associated with treatment. Patients received 4 cycles of TX. Tumor tissue obtained from Mammotome™ core biopsies pretreatment (BL) and post-Cycle 1 (C1) of TX was flash frozen and stored at -70C until processing. Gene expression analysis utilized Affymetrix HG-U133 Plus 2.0 GeneChip arrays. Statistical analysis was performed using BRB Array Tools after RMA normalization. Gene ontology (GO) pathway analysis used random variance t-tests with a significance level of p<0.005. For gene categories identified by GO pathway analysis as significant, expression levels of individual genes within those pathways were compared between classes using univariate t-tests; those genes with significance level of p<0.05 were reported. The analysis of baseline gene expression included baseline specimens from twenty-eight patients: 11 responders and 17 non-responders. Analyses of changes in gene expression included paired baseline and post-cycle 1 specimens from 14 patients; of these 6 patients were responders and 8 patients were non-responders.