The present invention provides methods of preventing or delaying the development of cancer (e.g., breast cancer) in BRCA1 mutation positive patients by beginning progesterone receptor antagonist treatment at an early age (e.g., by age 35, 30, or 25). In certain embodiment, such early treatment is long-term treatment, which may substitute or delay a preventative ovariectomy, single or double mastectomy (e.g., in patients wishing to delay or avoid a mastectomy, or patients that cannot afford a mastectomy).
