Volumetric modulated arc therapy versus three-dimensional conformal radiotherapy in breast cancer patients treated with regional nodal irradiation

Abstract Background We compared the dosimetric and clinical outcomes of VMAT and 3D-CRT in breast cancer patients undergoing regional nodal irradiation (RNI) to determine the effectiveness of VMAT. Methods This retrospective cohort study included breast cancer patients who underwent adjuvant radiotherapy with RNI between July 2016 and September 2022. Patients were assigned to receive either 3D-CRT or VMAT based on the laterality of their cancer. Right-sided breast cancer received 3D-CRT, while left-sided breast cancer received VMAT. Radiotherapy consisted of a dose of 50 Gy/25 fr to the chest wall or breast and the regional nodes. Dosimetric parameters, adverse events, and survival were compared between 3D-CRT and VMAT. Results A total of 126 patients were included in the analysis, with 64 in the 3D-CRT group and 62 in the VMAT group. VMAT showed better coverage of the clinical target volume (P < 0.01). Among patients who received internal mammary node irradiation, VMAT resulted in a lower total lung V20 Gy compared to 3D-CRT (17% vs. 11%, P < 0.01), whereas total lung V5 Gy was higher for VMAT (27% vs. 34%, P < 0.01). The incidence of grade 2 acute dermatitis was lower in the VMAT group (27%) than in the 3D-CRT group (47%) (P= 0.02). The 5-year overall survival and breast cancer-specific survival rates were 87% and 90% in the 3D-CRT group and 100% and 100% in the VMAT group, respectively (P = 0.06 and 0.09). Conclusions VMAT showed better target coverage and less acute radiation dermatitis compared to 3D-CRT.