Gabe Sonke, MD, PhD, from the Netherlands Cancer Institute, Amsterdam, Netherlands, discusses how to sequence treatment options in breast cancer at the European Cancer Congress of the European Cancer Organisation (ECCO) 2017 in Amsterdam, Netherlands. There are currently many options in the treatment of breast cancer, for example PI3 kinase inhibitors and CDK 4/6 inhibitors, such as ribociclib. However, Dr Sonke explains that there is a need for studies to determine the most effective sequence of these drugs, as drugs that may be effective as a first-line treatment may not be as effective for second-line.