Effects of chest wall compensation film thickness and patient's body characteristics on setup errors and dosimetry in intensity-modulated radiotherapy for breast cancer
Objective To investigate the effects of the thickness of the chest wall compensation film and the patient's body characteristics on the setup errors and radiation dose of breast cancer patients receiving intensity-modulated radiotherapy following surgery.Methods A total of 103 patients with breast cancer who were treated in the Tumor Radiotherapy Center of Fuyang Cancer Hospital from January 2021 to June 2023 were selected for a prospective study.All patients received cone-beam CT scan.The effects of body mass index(BMI),tumor location,chest circumference,and the affected breast volume on the setup errors were analyzed;and the effects of different compensation film thicknesses on the radiation doses to the planning target volume(PTV),lung,heart,and spinal cord were explored.Results The left-right setup errors didn't differ significantly in breast cancer patients with different BMI and affected sides(P>0.05);but the patients with chest circumference≥89.0 cm and affected breast volume≥650 cm3 had greater left-right setup errors than the other patients(chest circumference<89.0 cm and affected breast volume<650 cm3)(P<0.05).The difference in the superior-inferior setup errors was trivial in breast cancer patients with different affected sides(P>0.05),but the superior-inferior setup errors were greater in patients with BMI≥23.1 kg/m²,chest circumference≥89.0 cm,and breast volume on the affected side≥650 cm3 than the others(BMI<23.1 kg/m²,chest circumference<89.0 cm,and breast volume on the affected side<650 cm3)(P<0.05).There was no significant difference in the anterior-posterior setup errors in breast cancer patients with different BMI,chest circumferences,breast volumes,and affected sides(P>0.05).For left-sided breast cancer,the measured values of D95%and D5%of PTV,V20%of left lung,V30%and Dmean of heart,Dmax of spinal cord,MU,and HI in patients with 0.5 and 1.0 cm compensation films were close(P>0.05);while lower CI was found in patients with 0.5 cm compensation film than those with 1.0 cm compensation film(P<0.05).For right-sided breast cancer,the measured values of D95%and D5%of PTV,V20%of right lung,Dmax of spinal cord,MU,CI,and HI didn't differ significantly between patients using 0.5 and 1.0 cm compensation films(P>0.05).Conclusion The BMI,chest circumference,and breast volume on the affected side in breast cancer patients undergoing intensity-modulated radiotherapy are all associated with the setup errors.Both 0.5 and 1.0 cm chest wall compensation films can be used for postoperative radiotherapy,which has little effect on the dosimetry and accelerator MU.
breast cancerchest wallcompensation film thicknessbody characteristicsintensity-modulated radiotherapysetup errorradiation dose
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