Moreover, it was recently shown that RANKL serum levels are significantly increased in breast cancer patients who developed bone metastases (p = 0.01) and patients within the highest quartile of RANKL had a significantly increased risk of developing bone metastases compared to those in the lowest (HR 4.62, 95%CI 1.49–14.34, p = 0.03) (148). This evidence concerns the gene TNFSF11 and breast cancer.