Dosimetric comparison of treatment of left breast cancer using 3-dimention conformal radiotherapy technique (3D-CRT) and intensity-modulated radiotherapy technique (IMRT)

Abstract

Background: Breast cancer is the most common malignant cancer in women, and is the second leading cause of death from cancer in women, after lung cancer. This study compared the dose distribution of left breast as planning target volume (PTV), ipsilateral lung, contralateral lung, heart, and contralateral breast in whole left breast radiotherapy with two general methods, 3-dimention conformal radiotherapy technique (3D-CRT) and intensity-modulated Radiotherapy technique (IMRT) using treatment planning system. Methods: Computed tomography (CT) scan data of 30 patients with left breast cancer with average age of 46 years, candidates for radiotherapy of whole breast, were selected randomly. The left breast contoured as the target and ipsilateral lung, contralateral lung, heart, and contralateral breast contoured as organs at risks according to Radiation Therapy Oncology Group (RTOG) protocol. The 3D-CRT planned with using two tangential opposite beams, depended to patient's anatomy with or without a wedge and using energy of 6 MV. The IMRT treatment plan was optimized by three methods, IMRT-6Field, IMRT-7Field, and IMRT-9Field with energy of 6 MV. Finally, the dosimetric factors of target organ and organs at risk were derived from the dose-volume histogram (DVH) plot, and compared with each other. Findings: The IMRT techniques increased the mean dose of all organs compared to the 3D-CRT technique. From the dosimetric point of view, this was a good indication for target tissue. In the IMRT technique, the volume of the ipsilateral lung that coverage the high doses decreased, and the volume that coverage the lower doses increased compared to 3D-CRT technique. Homogeneity and conformance indexes in IMRT-9Field method were the best, and in 3D-CRT method were the worst among all methods. Conclusion: In general, the IMRT techniques are better than the 3D-CRT technique due to better coverage of the target volume, and volume reduction of the dose-receiving organ; there are no significant differences between the three IMRT techniques. © 2018, Isfahan University of Medical Sciences(IUMS). All rights reserved.