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

Abstract

<h3>Purpose/Objective(s)</h3> 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. <h3>Materials/Methods</h3> 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 (M_LR, M_AP, M_SI), and the distance between the innermost, foremost and uppermost of the CTV (DS_LR, DS_AP, DS_SI). <h3>Results</h3> M_AP, M_SI, and M_LR 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, M_AP and D × H are strongly correlated (r = 0.805); MSI is strongly linearly correlated with DS_AP, and DS_LR, correspondingly r(R²) values are 0.94(0.87), 0.91(0.80); M_LR and DS_AP, DS_SI, DS_LR 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, M_AP and DS_LR, M_SI and DS_AP all show strong linear negative correlation, r(R²) values are -0.96 (0.91) and -0.95 (0.87), while M_LR shows strong linear positive correlation with DS_LR, r(R²) values is 0.91 (0.77). <h3>Conclusion</h3> The mobility of the titanium clip is anisotropic (M_SI > M_AP > M_LR), 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