| Objective:To study the relationship between weight change and setup error and the trend of weight change in radiotherapy for patients with cervical cancer after surgery,and to find the population that needs to be monitored.Methods:A total of 40 patients with cervical cancer who received intensity modulated radiotherapy(IMRT)after surgery from October 2019 to October2020 were selected.Weight and setup errors were recorded once a week before radiotherapy,and body mass index was recorded and grouped(Normal +underweight group(BMI < 25),overweight group(25≤BMI < 30),obesity group(BMI ≥ 30)).One-way ANOVA was used for the difference of setup error between groups,the difference of weight loss ratio between groups was determined by Fisher’s exact probability method,one-way ANOVA was used to analyze the difference of setup error among groups with different weeks and weight loss degree,and Spearman method was used to analyze the correlation between weight change and setup error.Results:Weight and setup errors were measured 200 times in 40 patients.There was no statistically significant difference in the setup error between the normal+ underweight group and the overweight group(P > 0.05),while the setup errors of the obese group in the direction of X-axis and Z-axis were respectively different from those of the other two groups(P<0.05).Therefore,the patients were divided into the obese group and the non-obese group(The X-axis represents the left and right direction,the Y-axis represents the head and foot direction,and the Z-axis represents the abdomen and back direction).The weight loss rate of the obese group was 82.4%,while that of the non-obese group was 34.8%,and the difference between the two groups was statistically significant(P < 0.05),indicating that the obese group was more prone to weight loss during radiotherapy.The correlation analysis showed that the weight loss in the obese group was significantly positively correlated with the setup errors in the X and Z axis(P values in the X,Y and Z directions were0.002,0.448 and 0.040,respectively).The degree of weight loss and setup error in the obese group increased with the progression of the week,and the setup error also increases with the decrease of body weight.There were statistically significant differences in weight loss and setup error in the X-axis(P < 0.05).There was no correlation between weight gain and weight loss in non-obese group and setup error(P > 0.05),and the same was true for weight gain in obese group.The margin of CTV(clinical target volume)to be expanded was calculated from the measured setup error,all patients were able to meet the plan requirements for 5mm of CTV external expansion in the X and Z axis directions,but the setup error in the Y-axis direction was relatively large,expansion of 9.00 mm and 5.15 mm was required for obese and non-obese patients,respectively.Conclusions:For patients with cervical cancer undergoing IMRT after surgery,obese patients are more likely to lose weight,their setup error in the X and Z axis direction increases with the increase of weight loss.At the same time,the degree of weight loss and the setup error along the X-axis direction increased with the progress of the week.So their weight should be closely monitored.All patients could achieve the planned setup error in the X and Z axis directions,but the setup error in the Y-axis direction was relatively large,so the positioning method should be improved to limit the movement of the human body in the Y-axis direction. |
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