HER2-positive breast cancer is an aggressive subtype of breast cancer with patients having significantly lower survival rates compared to other breast cancers. HER2-positive breast cancer shows pathway addiction to multiple mitogenic signaling pathways. One strategy in cancer treatment is targeted drug therapy which inhibits the function of specific proteins along these signaling pathways Predicting drug sensitivity using a patient's tumor markers such as somatic mutations and copy number variation can help guide treatment selection toward the realization of precision medicine. The motivation for this work is to 1) characterize the degree of cross-phenotype response when a targeted inhibitor is applied and 2) identify potential oncogene collaborations that can drive the decisions of which targeted treatments should be used.