Mobility of Titanium Clamps in Radiotherapy Patients After Breast-Conserving Surgery and the Correlation With Breast Size and Position of Titanium Clamps

Purpose/Objective(s)To analyze the inter-stage mobility of titanium clamps in patients after breast-conserving surgery, to provide references for the margins of planning target volume (PTV), and to explore its relationship with breast size and titanium clamp's position.Materials/MethodsFifteen patients after breast-conserving surgery were randomly selected, using intensity modulated radiotherapy (IMRT), and CBCT twice a week for position verification; the basal surface diameter (D) and breast height axis (H) of the affected breast were measured at the tracheal bifurcation level of the localized CT. The clinical target area (CTV) is divided into 4 quadrants with the center of mass of the tumor bed as the origin. In each quadrant, record the movement of the titanium clamp in the left and right (LR), abdominal and back (AP), head and feet (SI) directions (MLR, MAP, MSI), and the distance between the innermost, foremost and uppermost of the CTV (DSLR, DSAP, DSSI).ResultsMAP, MSI, and MLR were as follows:1.1 ± 3.6 mm,0.8 ± 4.7 mm,2.2 ± 3.0 mm; the systematic error Σ and random error σ in the abdomen, back, head, feet, left and right directions were 2.0, 2.4, 2.9, 3.0, 1.7, 2.2 (mm) and 3.2, 4.0, 4.7, 4.7, 2.4, 4.0 (mm); Respectively, the margins of PTV were 7.2, 8.8, 10.5, 10.9, 5.9, 8.3 (mm). In the first quadrant, when D × H < 99.89 cm2, MAP and D × H are strongly correlated (r = 0.805); MSI is strongly linearly correlated with DSAP, and DSLR, correspondingly r(R2) values are 0.94(0.87), 0.91(0.80); MLR and DSAP, DSSI, DSLR are strongly linearly correlated, r(R2) values are 0.94(0.86), 0.91(0.80), 0.94(0.87). In the fourth quadrant, when D × H < 90.71 cm2, MAP and DSLR, MSI and DSAP all show strong linear negative correlation, r(R2) values are -0.96 (0.91) and -0.95 (0.87), while MLR shows strong linear positive correlation with DSLR, r(R2) values is 0.91 (0.77).ConclusionThe mobility of the titanium clip is anisotropic (MSI > MAP > MLR), the maximum extension range can reach 10.9 mm in the SI direction, and it is easily affected by the size of the breast and the position of the titanium clamp. [Keywords] breast cancer; breast conserving surgery; cone beam CT; titanium clip; radiotherapy To analyze the inter-stage mobility of titanium clamps in patients after breast-conserving surgery, to provide references for the margins of planning target volume (PTV), and to explore its relationship with breast size and titanium clamp's position. Fifteen patients after breast-conserving surgery were randomly selected, using intensity modulated radiotherapy (IMRT), and CBCT twice a week for position verification; the basal surface diameter (D) and breast height axis (H) of the affected breast were measured at the tracheal bifurcation level of the localized CT. The clinical target area (CTV) is divided into 4 quadrants with the center of mass of the tumor bed as the origin. In each quadrant, record the movement of the titanium clamp in the left and right (LR), abdominal and back (AP), head and feet (SI) directions (MLR, MAP, MSI), and the distance between the innermost, foremost and uppermost of the CTV (DSLR, DSAP, DSSI). MAP, MSI, and MLR were as follows:1.1 ± 3.6 mm,0.8 ± 4.7 mm,2.2 ± 3.0 mm; the systematic error Σ and random error σ in the abdomen, back, head, feet, left and right directions were 2.0, 2.4, 2.9, 3.0, 1.7, 2.2 (mm) and 3.2, 4.0, 4.7, 4.7, 2.4, 4.0 (mm); Respectively, the margins of PTV were 7.2, 8.8, 10.5, 10.9, 5.9, 8.3 (mm). In the first quadrant, when D × H < 99.89 cm2, MAP and D × H are strongly correlated (r = 0.805); MSI is strongly linearly correlated with DSAP, and DSLR, correspondingly r(R2) values are 0.94(0.87), 0.91(0.80); MLR and DSAP, DSSI, DSLR are strongly linearly correlated, r(R2) values are 0.94(0.86), 0.91(0.80), 0.94(0.87). In the fourth quadrant, when D × H < 90.71 cm2, MAP and DSLR, MSI and DSAP all show strong linear negative correlation, r(R2) values are -0.96 (0.91) and -0.95 (0.87), while MLR shows strong linear positive correlation with DSLR, r(R2) values is 0.91 (0.77). The mobility of the titanium clip is anisotropic (MSI > MAP > MLR), the maximum extension range can reach 10.9 mm in the SI direction, and it is easily affected by the size of the breast and the position of the titanium clamp. [Keywords] breast cancer; breast conserving surgery; cone beam CT; titanium clip; radiotherapy