Measurement of imposed radiation dose and normal tissue complications probability to lung and heart in patients with mastectomy using two common tangential radiotherapy methods of supraclavicular nodes, anterior-posterior (AP) and two parallel opposed fields (POFs)

Abstract

Background: The study aimed to evaluate imposed radiation dose and normal tissue complications probability (NTCP) of two common treatment plans of supraclavicular nodes, anterior-posterior (AP) field and parallel opposed fields (POFs) which are widely used in tangential treatment plans for patients with mastectomy. Methods: The stated methods were planned on the computed tomography (CT) scan images of a chest phantom, using TiGRT treatment planning system (TPS). Then, the normal tissue complications probability values were estimated using dose-volume histogram (DVH) data of the plans. According to the plans, the phantom was irradiated with 6 and 15 MV photon beams of a Siemens Primus linac. Dose measurements were also done using thermoluminescence dosimeters. Findings: The mean ± standard deviation (SD) dose to ipsilateral lung (P = 0.045) and heart (P = 0.078) for tangential beams with a single anterior-posterior field (35.42 ± 2.84 and 28.73 ± 3.17 percent, respectively) was significantly lower compared to tangential beams with parallel opposed fields (49.36 ± 2.35 and 30.41 ± 3.77 percent, respectively). In addition, the normal tissue complications probability values of ipsilateral lung and heart for tangential beams with anterior-posterior field (4 and 3, respectively) was lower compared to tangential with parallel opposed fields (6 and 4, respectively). Conclusion: It is considered that irradiating supraclavicular nodes with an anterior-posterior field is more suitable technique compared to parallel opposed fields, due to lower imposed dose, and also lower normal tissue complications probability to ipsilateral lung and heart of the patients. © 2018, Isfahan University of Medical Sciences(IUMS). All rights reserved.