ABSTRACT
Objective:To compare the differences of postoperative clinical target volume of internal mammary lymph node (CTV ImlN) by different delineation methods, and to explore the reasonable method of CTV ImlN delineation after internal mammary lymph node dissection (ImlND). Methods:A total of 20 breast cancer patients who had undergone modified radical mastectomy (MRM) with ImlND on the affected side and had complete preoperative and postoperative CT images were selected. The CTV (CTV pr-I, CTV pr-a) of both sides of ImlN were delineated on preoperative CT images according to RTOG guideline. On postoperative CT images, three different methods including deformation image registration (DIR) method, visual contrast method and precise measurement method, were employed to delineate the postoperative CTV ImlN of the affected side. The targets were named as CTV DIR, CTV V and CTV M, respectively. The central displacement, target volume, degree of inclusion (DI) and conformity index (CI) of CTV pr-a, CTV V, CTV M and CTV DIR were compared. Results:The central displacement of CTV V, CTV M and CTV DIR from CTV pr-a was 2.17 cm, 1.44 cm and 1.25 cm, respectively. The target volume of CTV pr-a, CTV pr-I, CTV V, CTV M and CTV DIR was 2.10 cm 3, 2.17 cm 3, 2.04 cm 3, 1.88 cm 3 and 2.07 cm 3 respectively. There was no significant difference in the target volume (all P>0.05). The CI values of CTV V-CTV pr-a and CTV M-CTV pr-a were both 0.16, and that of CTV DIR-CTV pr-a was 0.43. The CI value of CTV DIR was significantly higher than those of CTV V and CTV M (both P<0.01). The DI values of CTV V-CTV pr-a, CTV M-CTV pr-a and CTV DIR-CTV pr-a were 0.26, 0.24 and 0.58, respectively. The DI value of CTV DIR was significantly higher than those of CTV V and CTV M (both P<0.01). Conclusions:It is difficult to accurately delineate the CTV ImlN for patients after ImlND. However, the spatial position fitness of the target region delineated by DIR method is better than those by visual contrast and precise measurement methods.