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Objective:To study the change pattern of neck diameter and relevant factors in nasopharyngeal carcinoma (NPC) patients treated with helical tomotherapy, aiming to provide reference for clinical practice.Methods:Fifteen NPC patients treated with helical tomotherapy at Sun Yat-Sen University Cancer Center from November 2020 to February 2021 were enrolled in this study. The transverse diameters of NPC patients' neck contours and body weight of all patients during radiotherapy were recorded weekly. We used descriptive statistics to explore the distribution of transverse diameters of NPC patients' neck contours during radiotherapy. And Spearman correlation analysis was used to assess the association between weight loss and changes in neck contour transverse diameter.Results:During radiotherapy, the distribution of transverse diameters of NPC patients' neck contours was completely different from the initial values. Specifically, the transverse diameters were significantly reduced at the 4th week of the radiotherapy. Moreover, the reduction of transverse diameter of neck contour was highly correlated with the weight loss ( r=0.803, P<0.05), and moderately correlated with gender ( r=0.523, P<0.05). However, there was no statistical correlation between the alteration of neck diameter and age, TNM stage, and the mean dose of GTV nd-L, GTV nd-R, PTV nd-L and PTV nd-R (all P>0.05). Conclusions:The neck contours of NPC patients are altered regularly during helical tomotherapy, which are narrowed the most obviously in the 4th week. Extensive attention should be paid to the changes of neck contour during radiotherapy in clinical practice.
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Objective To comparatively analyze the acute adverse reactions of helical tomotherapy ( HT) and intensity-modulated radiation therapy ( IMRT) for nasopharyngeal carcinoma ( NPC) . Methods A total of 100 NPC patients treated with radiotherapy were selected and divided into the HT group ( n=50) and IMRT group ( n=50) . All patients were treated with concurrent chemoradiotherapy. The prescription dose of radiotherapy was DT 68.2-73.8 Gy/30-34F. The severity of acute adverse reactions of skin, oral mucosa, salivary glands and esophagus was evaluated with the established RTOG criteria. The differences between two groups were evaluated by paired t-test. Results The dose of organs at risk ( OARs) in the HT group was significantly lower than that in the IMRT group ( P<0.05) , whereas the dose of target area of PTVnx, PTVnd ( left) and PTVnd ( right) did not significantly differ between two groups ( all P>0.05) . In the HT group, the incidence rate of grade 0-3 acute adverse reactions in the skin, oral mucosa, salivary glands and esophagus were ( 14%, 68%, 18%, 0%) , ( 10%, 54%, 36%, 0%) , ( 0%, 74%, 26%, 0%) and ( 10%, 60%, 28%, 2%) , respectively. In the IMRT group, the corresponding results were ( 0%, 52%, 48%, 0%) , ( 0%, 58%, 42%, 0%) , ( 0%, 28%, 72%, 0%) and ( 0, 40%, 60%, 0%) , respectively. The severity of acute adverse reactions of skin, salivary glands and esophagus in the HT group was slighter than those in the IMRT group ( all P<0.05) , the acute adverse reactions in the oral mucosa were similar between two groups ( P>0.05) . In the HT group, the onset time of acute adverse reactions in the skin was later than that in the IMRT group ( P<0.05) , and the onset time of other adverse reactions was similar between two groups ( all P>0.05) . Conclusions Both HT and IMRT can meet the requirements of the dose distribution in the target area for NPC, whereas HT is superior to IMRT in terms of the protection of OARs protection, the severity and onset time of acute adverse reactions.
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Objective To evaluate the effect of helical tomotherapy (HT) megavoltage CT (MVCT) under different acquisition pitch and registration conditions upon the accuracy of radiotherapy for used nasopharyngeal carcinoma,aiming to provide reference for image-guided radiotherapy (IGRT) for nasopharyngeal carcinoma.Methods MVCT scans were performed on an anthropomorphic head& neck phantom which was simulated the positioning errors in the x,y and z direction.The obtained images were registered with the planning CT images.Acquisition pitch was set as the coarse,normal and fine modes.Registration conditions were set as bone registration,bone and soft tissue registration and full-image registration.Registration accuracy was determined by comparing the measured value with the preset value.The accuracy of radiotherapy under different acquisition pitch and registration conditions was statistically compared.Results The 3D errors of bone,bone and soft tissue and full-image registration under different acquisition pitch (coarse,normal and fine) were (1.51±0.47,1.54±0.35,1.81±0.53) mm and (1.41± 0.37,1.53±0.36,1.56±0.39) mm and (1.51±0.27,1.57±0.32,1.73±0.33) mm,respectively.The bone registration yielded the highest accuracy (P＜0.05).When the registration condition was set as bone registration,the accuracy of three acquisition pitch did not significantly differ (all P＞0.05).The fine mode of acquisition pitch possessed the highest stability,whereas required the longest time.Conclusion The acquisition pitch and registration conditions should be selected during HT MVCT based on the clinical requirement of each patient with nasopharyngeal carcinoma.