International Journal of Hematology and Oncology 2023, Vol 33, Num 4 Page(s): 130-138
Effects of Setup Errors on Dose Distribution for Tangential Wedge Field and Field-in-Field Techniques During Breast Irradiation

Aydan SONMEZ1, Cem ONAL1, Serhat SONMEZ1, Gungor ARSLAN1, Cem PARLAK1, Erkan TOPKAN1, Melek YAVUZ2

1Baskent University Faculty of Medicine, Department of Radiation Oncology, Adana, TURKEY
2Akdeniz University Faculty of Medicine, Department of Radiation Oncology, Antalya, TURKEY

Keywords: Breast cancer, Radiotherapy, Field-in-field technique, Setup errors
This study is aimed to evaluate the effects of setup errors on dose distribution for target volume and healthy tissue within the irradiated volume and also critical surrounding organs for breast radiotherapy (RT) using both the tangential field and the field-in-field (FIF) technique. Ten patients with breast cancer were enrolled. For each patients two plans were generated; tangential field plan and FIF-plan. The setup errors were simulated for a series of displacements of ±5 mm and ±10 mm in superior-inferior (x-axis), medial-lateral (y-axis), and anteriorposterior (z-axis) directions and dose volume comparisons were made both between and within groups. The most prominent changes were observed in setup errors at z-axis. In wedge plan, 10-mm setup error at the +z axis caused a significant decrease in tumor coverage compared with the plan with no setup error (96.5% vs. 99.2%; p= 0.01). The 5 and 10 mm setup errors at the +z-axis resulted in significantly higher healthy tissue doses in wedge plans compared with FIF plans. The setup errors along z-axis had a significant effect on the dose distribution for target volume and also to the lungs. The setup error in the isocenter should be kept strictly below 5 mm.