In a Dutch multicentre study of 6294 invasive breast cancer patients ≤50 years, the risk of contralateral breast cancer for BRCA1/2 carriers at a median follow-up of 12.5 years was shown to be 2–3 times higher compared to non-carriers (HR 3.31, 95% CI 2.41–4.55; p < 0.001 and 2.17, 95% CI 1.22–3.85; p = 0.01 respectively). This evidence concerns the gene BRCA1 and breast carcinoma.