Abstract
PurposeTo use cone-beam computed tomography (CBCT) imaging to determine the impacts of patient characteristics on the magnitude of geometric setup errors and obtain patient-specific planning target volume (PTV) margins from the correlated patient characteristics in whole breast irradiation (WBI).MethodsBetween January 2019 and December 2019, a total of 97 patients who underwent breast-conserving surgery, followed by intensity-modulated radiation therapy in WBI, were scanned with pre-treatment CBCT for the first three treatment fractions and weekly for the subsequent fractions. Setup errors in the left–right (LR), superior–inferior (SI) and anterior–posterior (AP) directions were recorded and analyzed with patient characteristics—including age, tumor location, body mass index (BMI), chest circumference (CC) and breast volume (BV)—to examine the predictors for setup errors and obtain specific PTV margins.ResultsA total of 679 CBCT images from 97 patients were acquired for analysis. The mean setup errors for the whole group were 2.32 ± 1.21 mm, 3.71 ± 2.21 mm and 2.75 ± 1.56 mm in the LR, SI and AP directions, respectively. Patients’ BMI, CC and BV were moderately associated with setup errors, especially in the SI directions (R = 0.40, 0.43 and 0.22, respectively). Setup errors in the SI directions for patients with BMI > 23.8 kg/m2, CC > 89 cm and BV > 657 cm3 were 4.56 ± 2.59 mm, 4.77 ± 2.42 mm and 4.30 ± 2.43 mm, respectively, which were significantly greater than those of patients with BMI ≤ 23.8 kg/m2, CC ≤ 89 cm and BV ≤ 657 cm3 (P < 0.05). Correspondingly, the calculated PTV margins in patients with BMI > 23.8 kg/m2, CC > 89 cm and BV > 657 cm3 were 4.25/7.95/4.93 mm, 4.37/7.66/5.24 mm and 4.22/7.54/5.29 mm in the LR/SI/AP directions, respectively, compared with 3.64/4.64/5.09 mm, 3.31/4.50/4.82 mm and 3.29/5.74/4.73 mm for BMI ≤ 23.8 kg/m2, CC ≤ 89 cm and BV ≤ 657 cm3, respectively.ConclusionsThe magnitude of geometric setup errors was moderately correlated with BMI, CC and BV. It was recommended to set patient-specific PTV margins according to patient characteristics in the absence of daily image-guided treatment setup.
Highlights
Whole breast irradiation (WBI) after breast conserving surgery has become an important treatment for earlystage breast cancer patients and locally advanced breast cancer patients after effective preoperative systematic therapy [1,2,3]
It requires stringent treatment verification to ensure planning target volume (PTV) coverage is accurately maintained while the doses to organs at risk (OARs) are within the tolerance [5]
We evaluated the correlation between set up errors and patient characteristics, including patients’ age, breast laterality, body mass index (BMI), CC and breast volume (BV)
Summary
Whole breast irradiation (WBI) after breast conserving surgery has become an important treatment for earlystage breast cancer patients and locally advanced breast cancer patients after effective preoperative systematic therapy [1,2,3]. Intensity-modulated radiation therapy (IMRT) is a widely used radiotherapy (RT) technique in. The dose distributions of IMRT delivered to the target volume can be highly conformal with steep dose gradients. It requires stringent treatment verification to ensure planning target volume (PTV) coverage is accurately maintained while the doses to organs at risk (OARs) are within the tolerance [5]. In breast RT, many setup error sources contribute to deviations from the planned dose distribution, such as setup inaccuracies of the whole patient and breast deformation [6]. For accurate dose delivery in RT, it is essential to correct target positioning with the help of image-guided radiation therapy (IGRT) techniques
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
