Enlargement of mediastinal masses on simulation films: a radiotherapeutic problem in the management of patients with Hodgkin's disease.

The size of the mediastinal mass on standard posterior-anterior chest radiograph in stage I and stage II Hodgkin's disease has both prognostic and therapeutic importance. But the actual treatment is based on the anterior-posterior supine simulation film. Problems arise when the prognosis (whether all the disease can be effectively contained in an irradiation port) and toxicity (more lung and heart irradiated or chemotherapy required) are changed when the mass is markedly enlarged on the radiation simulation films. Differences in the direction of the X-ray beam, distance from the subject, and patient position are shown to increase artificially the size of a mediastinal mass on simulation films. The staging and therapeutic implications are discussed.