Figure 2.

Representative “Beam’s Eye View” from a single anterior-posterior field from a modern course of postoperative radiotherapy (A) and out-of-date postoperative radiotherapy (B) for a patient with a completely-resected right upper lobe tumor found to have involved N2 nodes. The borders for the field on the right (B) were derived from the specifications of the Medical Research Council (MRC) Lung Cancer Working Party randomized trial of postoperative radiotherapy, a trial included in the PORT meta-analysis. The MRC study mandated coverage of the entire mediastinum, bilateral hila, bronchial stump, and, in the case of an upper lobe tumor, the bilateral supraclavicular fossae. These field specifications resulted in significantly higher volumes of normal heart and lung in the treatment field than what is currently acceptable. Additionally, with older radiotherapy equipment (such as Cobalt-60 units), less penetrating, lower energy beams were used, which resulted in higher superficial dose relative to the dose at the desired target depth. This created significant dose inhomogeneity with the highest dose level deposited in uninvolved lung, chest wall, and heart. Contoured normal structures seen in this figure are the lungs (purple), the heart (pink), and the esophagus (orange).