The utility of non‐axial treatment beam orientations for lower lobe lung cancers

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 ([Formula: see text]). 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. PACS number: 87.55.de