title: The utility of non-axial treatment beam orientations for lower lobe lung cancers.
abstract: Traditional treatment beams for non-small-cell lung cancer are limited to the axial plane. For many tumor geometries, non-axial orientations appear to reduce the dose to normal tissues (e.g. heart, liver). We hypothesize that non-axial beams provide a significant reduction in incidental irradiation of the heart and liver, while maintaining adequate target coverage. CT scans of twenty-four patients with lower lobe lung cancers were studied. For each patient, an opposed oblique axial beam pair and a competing non-axial opposed oblique pair were generated, both off-cord. The competing plans delivered comparable doses/margins to the GTV. DVHs and integral doses were computed for all structures of interest for the two competing plans. The integral dose was compared for axial and non-axial beams for each contoured organ using a paired t-test. Dose to the heart was significantly lower for the non-axial plans ( p = .0001). For 20/24 patients, the integral heart dose was reduced by using non-axial beams. In those patients with tumors located in the inferior right lower lobe, a lower dose to the liver was achieved when non-axial beams were used. There were no meaningful differences in dose to the GTV, lungs, or skin between axial and non-axial beams. Non-axial beams can reduce the dose to the heart and liver in patients with lower lobe lung cancers. Non-axial beams may be clinically beneficial in these patients and should be considered as an option during planning.
authors.affiliation: 21st Century Oncology, Asheville, NC, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Quaranta
authors.forename: Shiva K
authors.initials: SK
authors.lastname: Das
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Shafman
authors.forename: Kim L
authors.initials: KL
authors.lastname: Light
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Marks
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D004947:Esophagus / Q000528:radiation effects; D006321:Heart / Q000528:radiation effects; D006801:Humans; D021621:Imaging, Three-Dimensional; D008099:Liver / Q000528:radiation effects; D008168:Lung / Q000473:pathology / Q000528:radiation effects; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D012867:Skin / Q000528:radiation effects; D013116:Spinal Cord / Q000528:radiation effects