Correlation between the dose measured in the rectum and reference dose in three-dimensional brachytherapy for cervical cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To explore the correlation between the dose measured in the rectum and reference dose in three?dimensional brachytherapy ( 3DBT ) for cervical cancer, and to evaluate the significance of the dose measured in the rectum. Methods Fifty patients receiving radiotherapy for cervical cancer were selected, and 3DBT was performed after pelvic external beam radiotherapy. According to the rectal monitoring method recommended in the report ICRU38, in vivo monitoring was applied to obtain the dose measured in the rectum, reference point dose ( DICRU ) , and D2 cm3 , and the planned dose was obtained from the planning system. The differences in these values were determined by the paired t?test and correlation analysis was performed with Pearson test. Results The dose measured in the rectum was higher than the planned dose (3. 48 vs. 3. 25,P=0. 000), and lower than DICRU(3. 48 vs. 3. 71,P=0. 000) and D2 cm3(3. 48 vs. 3. 87,P=0. 002). A linear relationship existed between the dose measured in the rectum and the planned dose, with a deviation percentage of-20% to 40% and an average deviation of 8. 16%;63%of the patients with cervical cancer had a deviation of<± 10%;the maximum deviation was 60%. The dose measured in the rectum had a strong correlation with DICRU(r=0. 722), but a weak correlation with D2 cm3 ( r=0. 284) . Conclusions During 3DBT for cervical cancer, the dose measured in the rectum has certain deviations, but has a linear correlation with the planned dose. Both the dose measured and the planned dose underestimate the dose at the reference point in the rectum, and in vivo rectal monitoring may be an effective method for quality control.