ABSTRACT
Many tissues in children have a lower tolerance to radiation than adults, but in many cases, these children have relatively large target volumes, which, depending on the diagnosis, require significant doses . For breast cancer, the most common female adult cancer, we typically can produce a good treatment plan with little effort to spare the normal tissues of the lung, heart, and contralateral breast . For the most common male adult cancer, prostate cancer, the most important organs at risk (OARs), the rectum and bladder, are readily kept below their tolerance doses with the use of modern planning and delivery techniques . In lung cancer, the third most common adult cancer behind breast and prostate, when the target is localized and treatable, our dosimetric challenge is to keep the normal lung tissue below its tolerance dose . Depending on the location of the lung tumor, we may also be challenged to keep the spinal cord below its tolerance dose . Head and neck
cancer consistently presents the most challenging treatment planning exercise with several OARs to protect: parotid glands, spinal cord, mandible, airway, and brainstem, to name a few . In addition to these OARs, there may be multiple targets with different doses required . About 1 in 30 adult cancers are in the head and neck compared to 1 in 3 in the breast or prostate . Thus, although we do get our challenging cases when treating adults, they are generally infrequent and we are much more used to applying planning templates, which take little adjustment to produce a good plan .
