Comparative analysis of BT-474 vs. MCF-7 xenografts establishes the advantage of Trast-based targeting against an ErbB2+ tumor, and clearly demonstrates the enhancement of the Trast-NG/DOX efficacy by sequential post-treatment with a small dose (which by itself has no measurable effect on tumor growth; not shown) of the HSP90 inhibitor 17AAG. This evidence concerns the gene ERBB2 and neoplasm.