[Trastuzumab emtansine (Kadcyla(®)) approval in HER2-positive metastatic breast cancers]

HER2 (human epidermal growth factor receptor 2) is overexpressed in 15 to 20% of breast cancer. Anti-HER2 targeted therapies, notably trastuzumab, have transformed the natural history of this disease. Trastuzumab emtansine, consisting of trastuzumab coupled to a cytotoxic agent, emtansine (DM1), by a stable linker, has been approved in November 2013 by the European Medicine Agency. Trastuzumab emtansine targets and inhibits HER2 signaling, but also allows emtansine to be directly delivered inside HER2-positive cancer cells. It is indicated as single-agent in taxane and trastuzumab-pretreated HER2-positive breast cancer patients with metastatic and locally recurrent unresecable disease or relapsing within 6 months of the end of adjuvant therapy. This indication is based on the results of the EMILIA study, an open label phase III randomized trial comparing trastuzumab emtansine to lapatinib-capecitabine. The two primary endpoints were reached. The progression-free survival was 6.4 months in the lapatinib-capecitabine arm versus 9.6 months for the trastuzumab emtansine arm (HR=0.65; 95% CI=0.55-0.77, P<0.001). Overall survival at the second interim analysis was 25.1 months in the lapatinib-capecitabine arm versus 30.9 months in the trastuzumab emtansine arm (HR=0.68; 95% CI=0.55-0.85, P<0.001). Moreover, adverse events were more frequent in the lapatinib-capecitabine arm.