Comparison of dosimetric parameters of volumetric modulated arc therapy and three-dimensional conformal radiotherapy in postmastectomy patients with carcinoma breast

Objective: Our study was undertaken to compare the dosimetric parameters of volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) in postmastectomy patients with left-sided carcinoma breast. Study Design: This was a hospital-based cross-sectional study. Materials and Methods: Thirty plans were generated - VMAT with two partial arcs and field in field tangential 3DCRT plans. Results: In the 3DCRT plans, planning target volume (PTV) dose coverage was 2% higher compared with the VMAT plan 98.21 +/- 1.79 versus 96.30 +/- 2.62 (P = 0.028). The conformity index was better for the 3DCRT plan (0.97 vs. 0.95; P = 0.022), while the homogeneity index was worse for the VMAT plans (0.16 vs. 0.23; P = 0.057). However, the organ at risk sparing was better with the VMAT plans when compared to the 3DCRT plans. This was particularly relevant for the higher doses. The V20 Gy (34.94 vs. 24.42), V30 Gy (32.32 vs. 16.19), and V40 Gy (28.23 vs. 8.03) for the lung were significantly higher for the 3DCRT plans when compared to VMAT plans (P = 0.000). Similarly, the V20 Gy (29.88 vs. 12.79), V30 Gy (27.25 vs. 4.94), and V40 Gy (24.58 vs. 1.47) for the heart was significantly higher for the 3DCRT plans when compared to the VMAT plans (P = 0.000). The V5 Gy for lung (77.86 vs. 47.38) and heart (76.18 vs. 39.36) was significantly higher for the VMAT plans when compared to the 3DCRT plans (P = 0.000). Conclusion: VMAT is dosimetrically superior to the field-in-field 3DCRT for left-sided breast cancer patients owing to its comparable PTV coverage and better sparing of heart and lung.