Optimization of Whole-Breast Irradiation: A Dosimetric Comparison of 3D-CRT, IMRT, and VMAT in Left-Sided Breast Cancer

Objective To compare the dosimetric performance and planning efficiency of three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT) for whole-breast irradiation in left-sided breast cancer. Methods Twenty patients with left-sided breast cancer (stage I–IIA, pT1-2N0M0) were included. For each patient, 3D-CRT, IMRT, and VMAT treatment plans were generated and optimized. Parameters assessed included target conformity and homogeneity indices; organ-at-risk doses (heart, lungs, and spinal cord) and planning efficiency. Results VMAT demonstrated superior target conformity and dose homogeneity compared with both 3D-CRT and IMRT ( p < 0.001 for both). Compared with 3D-CRT, VMAT reduced cardiac high-dose exposure and ipsilateral lung V40. However, VMAT increased the maximum spinal cord dose and contralateral lung V5. Although 3D-CRT provided superior spinal cord sparing and avoided contralateral lung low-dose exposure but exhibited inferior target conformity. IMRT achieved comparable target coverage to VMAT but with lower planning efficiency. Conclusion VMAT is advantageous in target dose conformity, homogeneity, cardiac sparing, and delivery efficiency, supporting its use as a preferred technique for left-sided breast radiotherapy. Individualized optimization should be considered to mitigate low-dose contralateral lung and spinal cord exposure based on patient-specific anatomy.