Dosimetric Comparison of Three Radiotherapy Techniques in Irradiation of Left-Sided Breast Cancer Patients after Radical Mastectomy

Abstract

Introduction. This study is aimed at evaluating the dosimetric differences among target segmented planning (TSP), conventional 9-field intensity modulated radiation therapy (9FIMRT) planning, and volumetric modulated arc therapy (VMAT) planning for postmastectomy radiotherapy of left-sided breast cancer patients. Material and Methods. Fifteen left-sided breast cancer patients who underwent radical mastectomy were enrolled. In TSP, the planning target volume (PTV) was divided into four regions (supra/infraclavicular, chest wall, external mammary region, and internal mammary region), and each individual PTV region was treated with respective fixed fields. Results. The VMAT plans showed superior to PTV dose conformity index (CI), homogeneity index (HI), protection of the ipsilateral lung, monitor units (MUs), and maximum dose (Dmax) to the contralateral breast compared with TSP and 9FIMRT plans. The TSP provided better protection for Dmean of the heart and left ventricle (p<0.05). A dose for left anterior descending artery from the three techniques had no significant difference. Compared with the 9FIMRT plans, the V5Gy (%) and V10Gy (%) for the ipsilateral lung were significantly reduced with TSP and VMAT (p<0.05). The V5Gy (%) and V10Gy (%) for the ipsilateral lung turned out to be similar between VMAT and TSP techniques. Conclusions. Our study indicates that VMAT should be a better choice of radiotherapy for left-sided breast cancer patients after radical mastectomy. If VMAT is unavailable, 9FIMRT can achieve better CI and HI values and be more MU-efficient compared with TSP; however, TSP can effectively reduce the low dose volume of the ipsilateral lungs and heart.

A dosimetric and radiobiological evaluation of VMAT following mastectomy for patients with left-sided breast cancer

“…These OARs were protected by adjusting the priority values to reduce the maximum percent dose and scatter dose. Compared with our IMRT plans and other studies of VMAT plans, the mean dose to the heart was comparably lower in our VMAT plans, 5.2 ± 0.9 Gy, while it was 13.5 ± 5.0 Gy according to Zhang [ 17 ], 7.2 ± 2.3 Gy according to Zhao [ 18 ], 9.31 ± 1.62 Gy according to Hu [ 19 ], 11.9 ± 5.06 Gy according to Ma [ 20 ], 7.7 ± 1.1 Gy according to Xie [ 21 ] and 7.4 ± 1.4 Gy according to Wang [ 22 ],15.2 ± 2.2 Gy according to Nobnop [ 24 ], 9.3 ± 1.1 Gy according to Zhang [ 26 ]. The low and medium doses received by the heart were also significantly lower with the VMAT technique than with the IMRT technique, except for V 2.5 .…”

“…The results of our study indicated that both IMRT and VMAT provided good coverage of the target, while VMAT showed, with statistical significance, more conformity and more dose homogeneity in the target area of CW and IMN, compared with those of IMRT, by avoiding areas of under-dose, and at the same time eliminating areas of relative overdose. Our VMAT significantly reduced the near-maximum dose of the PTV of CW and IMN, which was 54.3 ± 0.2 Gy, as compared with 55.4 ± 1.7 Gy from a study by Zhang [ 17 ], and 56.64 ± 0.63 Gy from a study by Hu [ 19 ], 54.93 ± 0.87 Gy from a study by Ma [ 20 ]. Furthermore, the increase in the near-minimum doses, V 95% and V 100% were higher in the VMAT plans than in the IMRT plans: 48.7 ± 0.3 Gy, as compared with 48.5 ± 2.2 Gy from a study by Zhang [ 17 ], and 48.84 ± 0.41 Gy from a study by Hu [ 19 ] and 47.77 ± 0.35 Gy from a study by Ma [ 20 ].…”

“…Our VMAT significantly reduced the near-maximum dose of the PTV of CW and IMN, which was 54.3 ± 0.2 Gy, as compared with 55.4 ± 1.7 Gy from a study by Zhang [ 17 ], and 56.64 ± 0.63 Gy from a study by Hu [ 19 ], 54.93 ± 0.87 Gy from a study by Ma [ 20 ]. Furthermore, the increase in the near-minimum doses, V 95% and V 100% were higher in the VMAT plans than in the IMRT plans: 48.7 ± 0.3 Gy, as compared with 48.5 ± 2.2 Gy from a study by Zhang [ 17 ], and 48.84 ± 0.41 Gy from a study by Hu [ 19 ] and 47.77 ± 0.35 Gy from a study by Ma [ 20 ]. The values of HI and CN in our study signify that slightly better homogeneity and conformality of target coverage were attained in VMAT plans than in IMRT plans.…”

“…For the OARs, different results have been reported [16–25]. As a result of studies by Popescu [ 16 ], Zhang [ 17 ], Zhao [ 18 ] and Hu [ 19 ], VMAT decreases the dose to the ipsilateral lung, heart and contralateral breast/lung, relative to IMRT.. However, the research of Ma [ 20 ], Xie [ 21 ] and Wang [ 22 ] demonstrates that IMRT has dosimetric advantages in the heart and left lung, compared with VMAT plans.…”

A Comparative Dosimetric Study of Left Sided Breast Cancer After Breast Conserving Surgery With 3d-CRT and Vmat

“…Historically, breast radiotherapy treatment planning consisted of two-dimensional planning, used a fluoroscopic technique to establish treatment fields. This was followed by 3-D CRT with two conventional tangential radiotherapy fields [5].…”