Abstract
BackgroundTo determine the impact of body-mass factors (BMF) before radiotherapy and changes during radiotherapy on the magnitude of setup displacement in patients with head and neck cancer (HNC).MethodsThe clinical data of 30 patients with HNC was analyzed using the alignment data from daily on-line on-board imaging from image-guided radiotherapy. BMFs included body weight, body height, and the circumference and bilateral thickness of the neck. Changes in the BMFs during treatment were retrieved from cone beam computed tomography at the 10th and 20th fractions. Setup errors for each patient were assessed by systematic error (SE) and random error (RE) through the superior-inferior (SI), anterior-posterior (AP), and medial-lateral (ML) directions, and couch rotation (CR). Using the median values of the BMFs as a cutoff, the impact of the factors on the magnitude of displacement was assessed by the Mann–Whitney U test.ResultsA higher body weight before radiotherapy correlated with a greater AP-SE (p = 0.045), SI-RE (p = 0.023), and CR-SE (p = 0.033). A longer body height was associated with a greater SI-RE (p = 0.002). A performance status score of 1 or 2 was related to a greater AP-SE (p = 0.043), AP-RE (p = 0.015), and SI-RE (p = 0.043). Among the ratios of the BMFs during radiotherapy, the values at the level of mastoid tip at the 20th fraction were associated with greater setup errors.ConclusionsTo reduce setup errors in patients with HNC receiving RT, the use of on-line image-guided radiotherapy is recommended for patients with a large body weight or height, and a performance status score of 1–2. In addition, adaptive planning should be considered for those who have a large reduction ratio in the circumference (<1) and thickness (<0.94) over the level of the mastoid tip during the 20th fraction of treatment.
Highlights
To determine the impact of body-mass factors (BMF) before radiotherapy and changes during radiotherapy on the magnitude of setup displacement in patients with head and neck cancer (HNC)
Intensity-modulated radiation therapy (IMRT) has become increasingly popular because dose escalation to the target can be done while sparing adjacent normal tissues [1]
Van Herk et al [8] suggested a clinical target volume (CTV)- planning target volume (PTV) margin of 2.5 systematic error (SE) + 0.7 random error (RE) to ensure that 90% of patients in a population receive a minimum cumulative CTV dose of at least 95% of the prescribed dose
Summary
To determine the impact of body-mass factors (BMF) before radiotherapy and changes during radiotherapy on the magnitude of setup displacement in patients with head and neck cancer (HNC). Radiation therapy (RT) is commonly used as part of multiple modality treatment for hand and neck cancer (HNC). In HNCs, several factors such as the accuracy of the immobilization device, change in body contours, and tumor regression could lead to setup uncertainties during RT. Causes might be independent or related to the others All of these factors need to be minimized with the use of special approaches. Image-guided radiation therapy (IGRT) can be used to correct and quantify geometrical uncertainties for daily setup [2]. Adaptive radiotherapy (ART) is an approach used to correct for anatomic changes caused by tumor shrinkage or body weight loss during RT [5]. There is a need to investigate suitable indications for ART for patients with HNCs
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