Figure 1.

Comparison of radiosensitivity and proton relative biological effectiveness (RBE) in breast cancer cell lines. (A) Comparison of the survival fraction at 2 Gy (SF2) of X-ray or proton treatment across 11 human breast cancer cell lines. Data are presented as the mean ± SEM from three independent experiments and the differences between proton and X-ray results are evaluated by a student t-test; * p < 0.05; ** p < 0.01. (B) Comparison of SF2 for X-rays and protons between non-TNBC and TNBC groups. No significant differences between groups are seen. (C) Proton RBE values relative to megavoltage X-rays for ten BC cell lines at SF = 0.5 and SF = 0.1. (D) Comparison of RBE₁₀ values for BC cell lines. RBE₁₀ was calculated as the ratio of megavoltage X-ray doses to proton doses that yield 10% survival. RBE of each cell line was compared to 1.10 using a one-sample t-test; * p < 0.05.