Displacement of the lumpectomy cavity defined by surgical clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast-conserving surgery: a comparative study

Abstract

et al. Displacement of the lumpectomy cavity defined by surgical clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast-conserving surgery: a comparative study. Br J Radiol 2013;86:20130416. FULL PAPER Displacement of the lumpectomy cavity defined by surgical clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast-conserving surgery: a comparative study Objective: To compare the displacements of the lumpectomy cavity delineated by the surgical clips and the seroma based on four-dimensional CT (4D-CT) for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS). Methods: 14 breast cancer patients after BCS were recruited for EB-PBI and undertook 4D-CT simulation.On the 10 sets of the 4D-CT images, all the surgical clips in the cavity were delineated. The gross tumour volume (GTV) formed by the clips, the seroma, and both the clips and the seroma were defined as GTV c , GTV s and GTV c1s , respectively. The displacements of the centre of mass (COM) of the clips, GTV c , GTV s , GTV c1s and the selected clips in the three-dimensional (3D) directions were recorded and compared.Results: In the left-right, anterior-posterior and superiorinferior directions, the displacements were 2.20, 1.80 and 2.70 mm for the clip COM; 0.90, 1.05 and 1.20 mm for GTV c ; 0.80, 1.05 and 0.80 mm for GTV s ; and 0.90, 1.20 and 1.40 mm for GTV c1s , respectively. In the 3D directions, the displacements of the clip COM were greater than the GTV c , GTV s , GTV c1s , and the displacements of the clip COM, GTV c1s , GTV c and GTV s were significantly greater than the displacements of the selected clips (p,0.05). Conclusion:The displacements of the clip COM were greater than that of the GTV c , GTV s , GTV c1s and the four selected clips. The optimal internal target volume should be defined based on the boundary displacements. Advances in knowledge: When the GTV was delineated using the clips and/or the seroma, there was displacement difference between the lumpectomy cavity centre and the boundary for the EB-PBI. The optimal internal target volume should be defined based on the boundary displacements of the lumpectomy cavity.Previous studies have reported that approximately 70-80% of the in-breast tumour recurrences occurred in the vicinity of the tumour bed (TB) and that the absolute risk of ipsilateral breast recurrence away from the primary tumour site is approximately 1.5-3.5% [1][2][3][4]. Thus, for early-stage breast cancer patients after breast-conserving surgery (BCS), partial breast irradiation (PBI), treating only the lumpectomy cavity with a suitable margin, may achieve a similar local control rate and an overall survival rate to whole-breast irradiation treating the whole breast. Externalbeam partial breast irradiation (EB-PBI) is an important approach in PBI, and clinical research has demonstrated that EB-PBI can achieve excellent results after strict patient selection and accurate target volume delineation [5,6].Accur...

Interobserver Variability of Target Volumes Delineated in the Supine and Prone Positions Based on Computed Tomography Images for External-Beam Partial Breast Irradiation After Breast-Conserving Surgery: A Comparative Study

“…In other words, for patients with small breasts who underwent radiotherapy, the breast volume discrepancy may not lead to obvious morphological changes between the supine and prone positions after BCS. Furthermore, surgical clips are not always consistent with the boundary of the lumpectomy cavity (28,29). If the surgical clips are located close to the skin or the chest wall, the CTV would be further limited from the skin surface and gland-pectorale interface.…”

Effects of four‐dimensional simulation of boost radiation after breast conservation surgery: A prospective dosimetric and volumetric analysis

“…Although some studies have reported significant respiratory displacement of surgical clips in the superior-inferior and anteroposterior directions, we observed that the displacement of surgical clips during the extreme phases of respiration in free-breathing mode was insignificant in relation to the safety margin allotted around the CTV to accommodate internal motion. 25,26 This removes the need for an additional margin for internal target volume around the CTV, even when treatment planning is carried out using 3-D simulations.…”

Interobserver variability in the delineation of the tumour bed using seroma and surgical clips based on 4DCT scan for external-beam partial breast irradiation

“…Surgical clips are not always consistent with the edge of seroma and the boundary of the lumpectomy cavity [ 13 , 17 ]. Ding et al [ 13 ] measured the three dimensional displacements of the GTV C , the GTVs and the GTV C+S and found that in the LR, AP and SI directions, the displacements were 0.9 mm, 1.05 mm and 1.20 mm for GTV C ; 0.80 mm, 1.05 mm and 0.80 mm for GTVs; and 0.90 mm, 1.20 mm and 1.40 mm for GTV C+S , respectively. In other words, the three dimensional displacements of GTV C+S were greater than those of GTV C and GTV S .…”

“…The 10% ~ 90% phases of the 4DCT images were registered on the 0% phase images, which served as the basic phase image. The tumour beds were delineated from the ten sets of 4DCT images based on the clips, the seroma, and both the clips and seroma (termed TB C , TB S , TB C+S , respectively) according to a set of guidelines [ 13 ] (Figure 1 ). When the TB was delineated based on clips, we adjusted the window level and width to minimise the impact of seroma for contouring.…”