Dosimetric comparison of the simultaneous integrated boost in whole-breast irradiation after breast-conserving surgery: IMRT, IMRT plus an electron boost and VMAT.

Objectives: To compare the target volume coverage and doses to organs at risks (OARs) using three techniques that simultaneous integrated boost (SIB) in whole-breast irradiation (WBI) after breast-conserving surgery, including intensity-modulated radiation therapy (IMRT), IMRT plus an electron boost (IMRT-EB), and volumetric-modulated arc therapy (VMAT).

Methods: A total of 10 patients with early-stage left-sided breast cancer after breast-conserving surgery were included in this study. IMRT, IMRT-EB and VMAT plans were generated for each patient.

Results: The conformity index (CI) of the planning target volumes evaluation (PTV-Eval) of VMAT was significantly superior to those of IMRT and IMRT-EB (P < 0.05). The CI of the PTV Eval-boost of VMAT was better than that of IMRT (P = 0.018) and IMRT-EB (P < 0.001), while the CI of the PTV Eval-boost of IMRT was better than that of IMRT-EB (P = 0.002). The V5, V10 and Dmean in ipsilateral lung with VMAT were significantly higher than IMRT (P < 0.05) and IMRT-EB (P < 0.05). The Dmean, V5 and V10 in heart with VMAT were significantly greater than those of IMRT and IMRT-EB (P < 0.05). There was no significant difference in the OARs between IMRT and IMRT-EB (P > 0.05).

Conclusions: Considered the target volume coverage and radiation dose delivered to the OARs (especially the heart and lung), IMRT may be more suitable for the SIB in WBI than IMRT-EB and VMAT. Additional clinical studies with a larger sample size will be needed to assess the long-term feasibility and efficacy of SIB using different radiotherapy techniques.