A comprehensive dosimetric comparison in adjuvant radiotherapy for various regional lymph node irradiations of left-side breast cancer using volumetric modulated arc therapy

Breast cancer is the most common cancer among women worldwide. The purpose of this study was to investigate the dosimetric parameters of critical organs for various irradiation ranges in the treatment of left-side breast cancer. The irradiation planning target volume (PTV) range in this research was divided into four groups: whole breast irradiation (group 1), whole breast with SCF irradiation (group 2), whole breast with SCF and AXLN irradiation (group 3), and whole breast with SCF, AXLN and IMN irradiation (group 4). Each group included 20 patients. We analyzed the dose parameters for the various irradiation ranges in the treatment plans retrospectively. The prescription dose was 45 Gy in 25 fractions to the PTV. In terms of the left lung, the mean dose in the four groups was 7.29 ± 1.04 Gy in group 1, 8.94 ± 2.13 Gy in group 2, 10.20 ± 1.44 Gy in group 3, and 11.44 ± 1.20 Gy in group 4. The average V5Gy, V10Gy, and V20Gy values of the left lung and whole lungs for group 1 and group 2 plans, group 1 and group 3 plans, and group 1 and group 4 plans were statistically significantly different. In terms of the heart, the average dose was 2.50 ± 0.47 Gy, 2.58 ± 0.74 Gy, 3.00 ± 0.43 Gy, and 3.97 ± 1.14 Gy in the plans of groups 1 to 4, respectively. The average V5Gy of the heart was 6.90 ± 2.26 Gy in group 1, 7.75 ± 2.58 Gy in group 2, 8.43 ± 2.10 Gy in group 3, and 13.89 ± 2.88 Gy in group 4. The study demonstrated various RT irradiation areas for left-side breast cancer patients. The dosimetric results of this research showed that an extensive volume with regional nodal irradiation may have the potential to increase the risks of radiation pneumonitis and heart disease. The comprehensive dosimetric analysis performed in this study will be helpful for clinical oncologists and medical physicists in terms of clarifying treatment plans to identify the results of any planned irradiation.