Elective Clinical Target Volumes in Anorectal Cancer: An RTOG Consensus Panel Contouring Atlas

The advent of intensity modulated radiotherapy (IMRT) provides an opportunity to spare critical normal tissue. For patients receiving radiotherapy for anal or rectal cancer, small bowel and the femoral heads can often be better protected with IMRT than conventional techniques. However, the technology also presents a challenge to the radiation oncologist. IMRT demands a much more detailed understanding of target structures than a conventionally planned two to four field technique.