A new U.S. study is giving doctors hope that they could one day find a cure for breast cancer — the number one cause of cancer deaths in women.

The study published in the online journal Nature looks at the genetics of breast cancer. It finds that there are four major types of breast cancer and that one of those types has molecular similarities to ovarian cancer.

Doctors now will turn their attention to whether they can treat the breast cancer with the same drugs that are successfully used to battle ovarian cancer.

The World Health Organization says breast cancer kills about 450,000 people every year.