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Abstract
Background and purposeWe aimed to analyze the influence of target‐related and clinical factors on lung tumor motion based on four‐dimensional CT (4DCT), and clarify the motion based on subgroups in lung stereotactic body radiation therapy.Materials and methods4DCT image data of 267 tumors from 246 patients were analyzed. The coordinates in the left–right (LR), anterior–posterior (AP), and cranial–caudal (CC) directions of the center of mass (COM) of the gross tumor volumes in 10 phases of 4DCT were measured. The peak‐to‐peak COM displacement in the LR, AP, CC, and 3D directions was calculated. The influence of target‐related and clinical factors on tumor motion was evaluated using multivariate analysis.ResultsThe tumor segment location correlated with the tumor motion in each direction. Tumor size was predictive of tumor motion in the 3D (p = 0.023) and AP directions (p = 0.049). The tumor motion for metastatic tumors was smaller than that for primary tumors in the LR (p = 0.019) and AP directions (p = 0.008). The CC motion for pulmonary surgery recipients (3.8 ± 4.5 mm) was less than that for patients who had not undergone surgery (5.6 ± 5.4 mm), and no significant clinical factor was observed. BSA and BMI were positively correlated with the motion in the CC (p = 0.02) and LR directions (p = 0.002).ConclusionThe tumor segment location was a good predictor of tumor motion. A larger tumor tends to have a smaller motion. Patients with metastatic tumors or those who have undergone pulmonary surgery exhibited smaller and more unpredictable tumor motions, which required individual assessments. Thus, clinical factors can potentially predict tumor motion.
Highlights
We discovered that 95% of the tumors moved less than 3.7, 5.1, 16.4, and 16.7 mm in the LR, anterior–p osterior (AP), CC, and 3D directions, respectively
We first found that the tumor segment location was a good predictive factor for the tumor motion in Variables Surgery Cardiopathy body surface area (BSA) gross tumor volume (GTV)-EE Lobes
Patients with metastatic tumors or those who have undergone pulmonary surgery showed a smaller and more unpredictable tumor motion, which was poorly associated with the tumor location
Summary
Stereotactic body radiation therapy (SBRT) has become the standard of care for medically inoperable patients with early stage non-small cell lung cancer (NSCLC),[1,2] and has shown significant efficacy in pulmonary oligometastases in patients with lung cancer, whether or not they undergo resection.3–6 High biological dose delivery to patients requires a high conformal dose distribution around the target.[7]Respiratory-induced tumor motion is a well-established cause of inter-fraction and intra-fraction geometric uncertainty during radiation delivery.[8,9] RTOG0813 and RTOG0915 trials recommended a 0.5-cm margin in the axial plane and a 1.0-cm margin in the longitudinal plane to accounting for tumor motion based on conventional 3DCT for lung SBRT.[10,11] The uniform margin may not represent the individual tumor motion, and result in a geographical miss or normal tissue unnecessarily irradiated, which may lead to high risk of radiation-related side effects.[2]. Whether a 4DCT scanning could provide a reliable tumor motion for treatment has been controversial.[15,16] The tumor motion magnitude could be influenced by target-related (e.g., size and location) and clinical factors (tumor origin and history of pulmonary surgery).[17] Understanding the tumor motion magnitude for different patient subgroups and using this information in constructing ITVs is crucial. We aimed to analyze the influence of target-r elated and clinical factors on lung tumor motion based on four-d imensional CT (4DCT), and clarify the motion based on subgroups in lung stereotactic body radiation therapy. Results: The tumor segment location correlated with the tumor motion in each direction. Patients with metastatic tumors or those who have undergone pulmonary surgery exhibited smaller and more unpredictable tumor motions, which required individual assessments.
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