In this large-scale MR analysis of 122,977 cases and 105,974 controls for breast cancer and 79,148 cases and 61,106 controls for prostate cancer, we investigated the effect of three common LDL-C-lowering drug targets (HMG-CoA reductase, NPC1L1, and PCSK9) on the risks of breast cancer and prostate cancer. This evidence concerns the gene NPC1L1 and Familial prostate cancer.