For PC patients treated with definitive (chemo)radiotherapy, pretreatment MTV2.5 volume achieved the best predictive value for primary recurrence, and the same value was also a prognosticator for DFS.

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.

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A combination of four-dimensional computed tomography with 18F-fluorodeoxyglucose positron emission tomography (4D CT-FDG PET) was used to delineate gross tumor volume (GTV) in esophageal cancer (EC). Eighteen patients with EC were prospectively enrolled. Using 4D images taken during the respiratory cycle, the average CT image phase was fused with the average FDG PET phase in order to analyze the optimal standardized uptake values (SUV) or threshold. PET-based GTV (GTVPET) was determined with eight different threshold methods using the auto-contouring function on the PET workstation. The difference in volume ratio (VR) and conformality index (CI) between GTVPET and CT-based GTV (GTVCT) was investigated. The image sets via automatic co-registrations of 4D CT-FDG PET were available for 12 patients with 13 GTVCT values. The decision coefficient (R2) of tumor length difference at the threshold levels of SUV 2.5, SUV 20% and SUV 25% were 0.79, 0.65 and 0.54, respectively. The mean volume of GTVCT was 29.41 ± 19.14 ml. The mean VR ranged from 0.30 to 1.48. The optimal VR of 0.98, close to 1, was at SUV 20% or SUV 2.5. The mean CI ranged from 0.28 to 0.58. The best CI was at SUV 20% (0.58) or SUV 2.5 (0.57). The auto-contouring function of the SUV threshold has the potential to assist in contouring the GTV. The SUV threshold setting of SUV 20% or SUV 2.5 achieves the optimal correlation of tumor length, VR, and CI using 4D-PET/CT images.