Interfraction Displacement of Primary Tumor and Involved Lymph Nodes Relative to Anatomic Landmarks in Image Guided Radiation Therapy of Locally Advanced Lung Cancer

摘要: Purpose To analyze primary tumor (PT) and lymph node (LN) position changes relative to each other anatomic landmarks during conventionally fractionated radiation therapy for patients with locally advanced lung cancer. Methods Materials In 12 non-small cell cancer PT, LN, carina, 1 thoracic vertebra were manually contoured on weekly 4-dimensional fan-beam CT scans. Systematic random interfraction displacements of all structures identified in the 3 cardinal directions, resulting setup margins calculated. Time trends effect volume analyzed. Results Three-dimensional displacement vectors systematic/random smaller carina than both PT LN. For mean (SD) 3-dimensional carina-based alignment 7 (4) mm versus 9 (5) bony anatomy ( P P= .002) compared using (8 [5] mm). Primary LN bone independent P> .05). Displacements between =.04) =.01) significantly correlated regression. change =.03). Conclusions Carina-based results a more reproducible setup. Considering independence impact regression over time, repeated imaging even PT-based is recommended disease.