The effective dose to circulating immune cells (EDIC) is associated with survival. This study from Institut Curie compared VMAT and IMPT in EDIC in patients with locally advanced breast cancer (BC). Based solely on static dosimetric data calculation, this study reported that IMPT reduced EDIC for both left-sided BC patients (3.15 Gy VMAT vs 1.65 Gy IMPT, p < 0.01), and right-sided BC patients (5.60 Gy VMAT vs 3.38 Gy IMPT, p < 0.01). Integral dose reduction was the main driver of EDIC reduction with IMPT and was associated with lung sparing for left-sided BC patients or liver sparing for right-sided BC patients.