IGF1 and breast cancer: The present MR results for IGF‐1 and breast cancer based on BCAC data are similar to those obtained from another MR study also based on BCAC data which showed an OR of 1.05 (95% CI 1.01‐1.10) per 5 nmol/L increase of genetically predicted IGF‐1 levels based on 265 SNPs associated with serum IGF‐1 levels in women.33