Creating cardiac substructure margins and treatment plan optimization in LUNG cancer and left breast radiotherapy

In thoracic irradiations, the coronary arteries (CA) are involuntarily exposed to radiation and subsequent cardiovascular toxicities may occur. To avoid this, the importance of accurately creating the safety margins (SM) of CA and determining the doses they receive has been recognized in recent years. Therefore, in the first part of study; Using electrocardiography-gated intravenous contrast-enhanced computed tomography (CT), CA (left coronary artery; LCA, left anterior descending artery; LAD, circumflex artery; Cx, right coronary artery; RCA) were divided into sections over cardiac CTs obtained from patients without cancer, SM were obtained by measuring their diameter and displacement (d). In the second part of the study; Using calculated this SM, the new treatment plans (NTP) resulting from the inclusion of LAD contour in the optimization (Op) treatment plans of previously treated lung cancer (LC) and left breast cancer (LBC) patients, were compared with the standard treatment plans (STP). While the maximum d of LCA, LAD1 and RCA2 were in the radial, the maximum d of Cx2 and LAD2 were in the craniocaudal direction, no generalization could be made in other parts. SM (mm), sagittal, transversal and vertical axes; In breath-hold planning CTs, LAD1 (upper section) 10, 6, 4; LAD2 (middle section) 2, 2, 5; LAD3 (lower section) 4, 8, 6; In planning CTs with internal target volume or free breath; LAD1 9, 5, 4; LAD2 2, 1, 4; LAD3 is 3, 7, 5 were found. In NTP; While no significant difference can be observed in the doses received by the targets and other critical organs, LAD V15 Gy, heart mean dose in LC cases, LAD V15 Gy, heart V25 Gy, heart V10 Gy in LBC cases, decreased significantly. Hence, it was concluded that LAD should be included in the Op by giving SM.