Why does hormone therapy work for some breast cancers but not others? Breast cancer expert Robert Carlson, MD, of the Stanford Comprehensive Cancer Center, explains the role of estrogen and progesterone some breast cancers in this video from the National Comprehensive Cancer Network (NCCN). NCCN, a not-for-profit alliance of 21 leading cancer centers—including Stanford—is dedicated to improving the quality and effectiveness of care for cancer patients. For more information on breast cancer and other cancers, including the NCCN Guidelines for Patients, visit www.NCCN.com.