3D conformal radiotherapy in the sagittal plane for centrally located thoracic tumors

Abstract

One hundred patients, recently treated at the University of California, San Francisco (UCSF) with radiotherapy for lung and esophageal cancer, were studied. Three subsets of these patients were defined based on tumor location to test how commonly the use of three-dimensional (3D) conformal radiotherapy (3DCRT) could improve significantly the delivery of high dosages. Comparisons were made between isodose distributions and dose volume histograms (DVHs) of patients' prior computed tomography (CT)-based treatment plans and newly generated 3D-based treatment plans. The use of beam angles outside the conventional horizontal plane did not significantly improve the dose distribution for patients if a peripheral mass was the target volume. Patients with a target volume involving the central thorax represented a subset (>40% of the patients) who would have benefited the most from the use of nonconventional beam angles. In these patients, sagittal coplanar beams (sagittal Y technique) reduced the dose to 30% of the lung volume from 30% to 5%. Doses to the spinal cord and heart were slightly higher than with conventional techniques but were within the tolerance of normal tissues. The sagittal Y technique allows an escalation in total dose to the tumor without increasing dose to normal tissues beyond their tolerance.