A cooperative group is a research project of the National Cancer Institute (NCI) that brings together many investigators from hospitals and academic research centers throughout the United States. There are currently nine cooperative groups funded by the NCI to study adult cancers. RTOG is one of these groups.

The goal of each of the cooperative groups is to bring the combined talents and resources of many institutions together to improve the treatment options for patients with cancer. The cooperative group members elect officers, form research committees, design research studies, enroll patients on these studies, analyze the research data, and publish the results in peer-reviewed national publications. Each group designates a Headquarters for data management, statistical analysis, and administrative review procedures. Each cooperative group continually monitors its members and their patient records to insure that the research studies are conducted safely and that the research data is accurate.