US Oncology was formed in 1999 through the merger of American Oncology Resources and Physician Reliance Network. US Oncology was founded in 1992 as American Oncology Resources. US Oncology is America's premier cancer care services company.US Oncology is America's premier cancer care services company. US Oncology supports the cancer care community by providing medical oncology services, cancer center services and cancer research services. US Oncology provides comprehensive services to a network of affiliated practices comprising more than 900 affiliated physicians in over 490 sites, including 81 integrated cancer centers, in 32 states. US Oncology estimates that in 2003 those physicians provided care to approximately 500,000 patients, including approximately 190,000 new patients. US Oncology's network's community-based focus allows its affiliated physicians to provide to patients locally the latest advances in therapies, research and technology, often within a single outpatient setting. As a result, patients access high-quality treatment with the least amount of disruption to their daily lives. The company's nationwide presence enables it to rapidly implement best practices and share new discoveries, and its network's size affords competitive advantages in areas such as purchasing, information systems, access to clinical research and leading edge technology.