CT-scan based localization of the internal mammary chain and supra clavicular nodes for breast cancer radiation therapy planning.

ABSTRACT

BACKGROUND AND PURPOSE: To evaluate the influence of the position and the exact localizations of supra clavicular nodes (SCN) and internal mammary chain (IMC) and their variability among patients in order to improve treatment planning in breast cancer (BC) patients. PATIENTS AND METHODS: A total of 46 CT scans of the chest were examined. All patients were female treated with breast conserving surgery and radiotherapy. The study was divided into two phases. The first consisted of measurements on 20 diagnostic CT scans, performed in the supine position with both arms over the head. All patients received contrast. This first phase was performed as a training program for radiologist and radiation oncologist to prepare for the second phase of the study 26 CT scans in treatment position on angled board without injection. For this second group, patients had one arm raised above the head (treated side) and the other kept by the side (contralateral side). Measurements were performed on both sides to evaluate the influence of the arm position. The depths of IM- and SC vessels were measured at five points (1) the origin of the internal mammary artery, (2) the sterno-clavicular articulation, (3-5) the first, second and third rib interspaces (RI). Measurements of the depth and of the distance between the internal mammary vessels and the middle axis of the sternum were obtained using electronic calipers on a PACS workstation. RESULTS: There were important individual variations of the depth of SCN, as follows 20-84 mm (diagnostic) and 19-64 (treatment position). No differences in the depth of the IMC were found between treated and contralateral side at the region of the I, II, and III rib interspaces. The lateral margin of the IMC was never more than 40 mm from the middle axis of the sternum (I, II, III rib interspaces). There was no difference in the lateral limits of IMC (the distance between the IM vessels and the middle axis of the sternum) between the two sides treated and contralateral. CONCLUSIONS: This study shows the importance of the patients' individual anatomy, their position and the large variability in the depth of SCN. It is important to visualize these regions to permit individual dosimetric optimization.