a b s t r a c tPurpose: To our knowledge, no study has specifically assessed the time course of anxiety during radiotherapy (RT). The objective of this study was to assess anxiety time courses in patients with nonmetastatic breast cancer. Material and methods: This multicenter, descriptive longitudinal study included 213 consecutive patients with breast cancer who completed visual analog scales (VASs) assessing state anxiety before and after the RT simulation and the first and last five RT sessions. Results: Pre-and post-session anxiety mean levels were highest at the RT simulation (respectively, 2.9 ± 2.9 and 1.6 ± 2.5) and first RT session (respectively, 3.4 ± 2.9 and 2.0 ± 2.4), then declined rapidly. Clinically relevant mean differences (P1 cm on the VAS) between pre-and post-simulation/session VAS scores were found only for the RT simulation (À1.3 ± 2.7; p < 0.001) and first RT session (À1.4 ± 2.4; p < 0.001). Five percent to 16% of patients presented clinically relevant anxiety (pre-and post-simulation/session VAS scores P 4 cm) throughout treatment. Conclusions: To optimize care, RT team members should offer all patients appropriate information about treatment at the simulation, check patients' understanding, and identify patients with clinically relevant anxiety requiring appropriate support throughout RT.