Patent ID: 8563603

Claim:
A method for the treatment of breast cancer in a mammal comprising administering to said mammal a composition comprising a pharmaceutically effective amount of a compound of the following formula: or a pharmaceutically acceptable salt thereof, wherein: X is —O—; Y is —O—; each R 1 and R 3 may be the same or different and, at each occurrence are independently an optionally substituted C 1-6 alkyl or wherein: R 6 , R 7 , and R 8 are independently selected from the group consisting of: hydrogen and —OR y , R y is at each occurrence, independently selected from hydrogen and optionally substituted C 1-6 alkyl, where two or more R y groups can be taken together with their intervening atoms to form a ring; and each R 4 may be the same or different and is hydrogen or optionally substituted C 1-6 alkyl, wherein said compound present in said composition is substantially pure.