Wing H Tong1,2, Yiwei Liu3. 1. Department of Public Health and Primary Care (PHEG), Leiden University Medical Center, Leiden, The Netherlands. w.h.tong@lumc.nl. 2. Argos Zorggroep "DrieMaasStede", Center for Specialized Geriatric Care, Schiedam, The Netherlands. w.h.tong@lumc.nl. 3. Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.