Companion diagnostics for Trastuzumab based neoadjuvant therapy: Two is better than one

Total sales of oncology drugs in 2017 was >USD50 billion and Herceptin was the 3rd top selling drug with about USD7 billion sales. Her2+ breast cancer is forecasted as the highest-growing segment of breast cancer treatment market to increase by 2.5 fold by 2023. Herceptin has a compound annual growth rate of 9.88% going from $4.95 billion in 2013 to $12.7 billion in 2023. While Trastuzumabbased chemotherapy has shown remarkable clinical benefits for HER2-positive breast cancer patients, a subset of patients (30-40%) shows little or no effect. This highlights an important clinical need for biomarkers in addition to Her2 for better stratification of patients for precision medicine of Her2+ breast cancer. Her2+ breast cancer is associated with an amplification of the HER2 locus in chromosome 17q. We hypothesized that HER2 and its co-amplified genes in C17q not only form a molecular network but also cooperatively and functionally contribute to the phenotype of Her2+ breast cancer.