Although larger and prospective studies are warranted to draw definitive conclusions, these results, taken together with the available evidence regarding pertuzumab and T-DM1 in first and further lines, as well as the prescription limitations concerning pertuzumab, may support the use of P + T + taxane as up-front treatment of metastatic HER2+ breast tumors independently from TTR. This evidence concerns the gene ERBB2 and breast neoplasm.