Objective: Comparative study of dose parameters of Volumetric modulated arc therapy (VMAT) and three-dimension radiotherapy (3D-CRT) in patients after left breast surgery with radiation therapy with regional lymph nodes. Materials and Methods: Twenty-four plans of 12 left-breast cancer patients were treated with VMAT with 4 partial arc and 3D-CRT plans were added to compare each other, from 1/2018 to 3/2019 at the Vinmec TimesCity International Hospital. Results: The average coverage dose to the treatment volume (PTV) of VMAT plans is better than the 3D-CRT plan (99.10 ± 0.17% compared to 98.7 ± 0.34%
p = 0.01). Conformity index (CI), homogeneity index (HI) for VMAT plans also better results CI: 0.99 vs. 0.98
p = 0.26 and HI: 0.096 compared to 0.119
p = 0.02). Organs at risk, at low doses V5Gy, V10Gy VMAT plans do not avoid good doses by 3D-CRT plans: V5Gy for left lung (78.8 ± 4.6% compared to 55.37 ± 4.38%) and heart (77.15 ± 9.52% compared to 19.15 ± 7.93%) (p <
0.001). However, at high doses, 3D-CRT plans are much higher than VMAT: Dose to left lung V20Gy (36.22 ± 3.9% compared to 22.62 ± 2.43%), V30Gy (30.6 ± 5.97% compared to 11.77 ± 2.53%) and V40Gy (24.73 ± 8.59% compared to 3.63 ± 2.02%) (P <
0.001). Similarly, the cardiac arrival dose of the 3D-CRT plan is higher than that of VMAT: V20Gy (11.54 ± 5.83% compared to 9.49 ± 6.00%, p>
0.05), V30Gy (9.25 ± 5.56% compared to 2.13 ± 1.89%) and V40 Gy (7.54 ± 5.03% compared with 0.2 ± 0.25%). Dose to coronary arteries also decreased significantly for VMAT plans compared to 3D-CRT: V20Gy (0.8 ± 1.01% compared to 27.29 ± 15.19%) V30Gy (0.00% compared to 23.09 ± 10.73%). Conclusion: VMAT is dosimetrically superior to the 3D-CRT for left‑sided breast cancer patients with regional nodes by dose coverage to PTV and good ability to avoid heart and lung and coronary arteries than