IGFBP2 and breast cancer: For all-cause and breast cancer-specific mortality, no heterogeneity of effects was observed by race/ethnicity for IGF1 (P for interaction 0.26 and 0.45, respectively), IGF1R (P for interaction 0.43 and 0.72), or IGFBP2 (P for interaction 0.49 and 0.32).