This specific study involved early research done in cells and mice, not humans.
The results are not ready for use in young women at high risk for breast cancer.
The research focused only on BRCA1. If the drug is effective, it's uncertain how generalizable this will be for women with mutations in other genes or average risk women.
There are ongoing clinical trials of the RANK ligand inhibitor denosumab for breast cancer. Results are not known as yet.