Relationship between tumor biomarkers and efficacy in TH3RESA, a phase III study of trastuzumab emtansine (T-DM1) vs. treatment of physician's choice in previously treated HER2-positive advanced breast cancer

Resumen:
Consistent with other reports, benefit was seen with T-DM1 regardless of PIK3CA mutation status. In a multivariate analysis including an interaction term (treatment group by log2-transformed HER2 mRNA), patients with higher HER2 mRNA levels benefited more from receiving T-DM1 (HR, 0.84; 95% CI, 0.75-0.94; interaction p value¿=¿0.0027). In summary, T-DM1 prolonged median PFS in all biomarker subgroups analyzed, including activating PIK3CA mutations, with numerically greater benefit in patients with tumors expressing HER2 mRNA >median vs. ¿median.