A typical primary care physician who treats elderly Medicare patients must coordinate care with 229 other physicians working in 117 different practices, according to a study by researchers at the Center for Studying Health System Change, Memorial Sloan-Kettering Cancer Center, and the Dana-Farber Cancer Institute. "The logistical challenges to care coordination are daunting given the fragmentation of care and the large number of peers that physicians must interact with when treating Medicare patients," said Hoangmai H. Pham, MD, MPH, the study's lead author and an HSC senior health researcher.