Interobserver variability in the delineation of the target volume based on supine and prone simulation 3DCT for external-beam partial breast irradiation after breast-conserving surgery / 中华放射肿瘤学杂志

ABSTRACT

Objective:To explore the interobserver variabilities in the delineation of the target volume using simulation three-dimensional computed tomography (3DCT) between the supine and prone positions for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS).Methods:Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study. All patients underwent axial 3DCT simulation scanning in the supine and prone positions during free breathing. Based on two different simulation 3DCT acquired, the gross target volume (TB) formed by using surgical clips and the clinical target volume (CTV) were delineated by five radiologists using specific guidelines. The following parameters including the target volume, coefficient of variations (COV) and matching degree (MD) were calculated to analyze the interobserver variability. Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study.Results:Whether in the supine or prone position, the interobserver variabilities for TB and CTV were statistically significant ( P<0.001, P=0.001, P<0.001, P=0.001). And the intersection of CTV in the prone position was 5.79 cm 3 greater than that in the supine position ( P=0.011). The interobserver variability of COV CTV in the prone positionwas significantly lower than that in the supine position ( P=0.014). And the interobserver variabilities of MDTB TB and MDTB CTV in the prone positionwere statistically greater than those in the supine position, respectively ( P<0.001, P= 0.001). Conclusions:When delineating the target volume of EB-PBI in the prone position, the interobsever variability can be reduced compared with that in the supine position. Hence, it is more reasonable to carry out EB-PBI in the prone position in free breathing.