Correlation of Mediastinal Metastatic Lymph Nodes Displacement With Primary Tumor Displacement and Adjacent Organs Based on 4DCT in Non-Small Cell Lung Cancer

Abstract

To investigate the correlation of intra-fraction displacement of the mediastinal metastatic lymph nodes with displacement of primary tumor and rates of volume change of lung and heart based on four-dimensional computed tomography (4DCT) for non-small cell lung cancer (NSCLC) Twenty-six patients diagnosed as NSCLC with fifty-one mediastinal metastatic lymph nodes were scanned by 4DCT simulation during free breathing. The left group (1L, 2L, 4L, 5 region) and right group (1R, 2R, 4R region) and under group (7, 9 region) mediastinal metastatic lymph nodes and primary tumor, heart, bilateral lungs were contoured on CT images of 10 phases separately. Then the displacement of the lymph nodes and primary tumor at left-right (LR), anterior-posterior (AP) and superior-inferior (SI) direction were measured. And the rates of volume change of lung and heart were acquired on the whole respiratory cycle. Comparison and correlation analysis were performed between displacement of the lymph nodes and the primary tumor as well as the correlation of the displacement with the rates of volume change of lung and heart. In the LR and AP directions, the correlation was significant between the displacement of the left group of lymph nodes and the ipsilateral primary tumor (r = 0.965, 0.897; p = 0.008, 0.015). It was significant correlation of displacement of the left group of lymph nodes in LR and the right group in AP with rates of volume change of ipsilateral lung (r = 0.609, 0.645; p = 0.035, 0.024). There were significant correlations between displacement of the left group lymph nodes and rates of volume change of heart in LR, AP and SI directions (r = 0.614, 0.897, 0.607; p = 0.044, 0.015, 0.037). There was no difference between the displacements of primary lung tumor and the lymph nodes in three directions during free breathing. The displacement of left primary lung tumor was able to predict displacement of left mediastinal lymph nodes of trachea in the LR and AP directions. Meanwhile, it was reasonable to predict three-dimensional lymph node motion by monitoring the rates of volume change of ipsilateral lung and heart for the mediastinal lymph nodes located in 1L, 2L, 4L, and 5 regions.