Ray has written about the anti estrogenic properties of the fat soluble vitamins, and here are some in vivo studies that show vitamin A both reduces breast cancer incidence and inhibits tumor growth even after being administered with a significant delay after tumor induction.
http://www.ncbi.nlm.nih.gov/pubmed/3123084
http://www.ncbi.nlm.nih.gov/pubmed/7083156
If you are interested in learning more just search PubMed for "retinol aromatase" and it will give you some studies explaining the anti-estrogenic mechanism of action for retinol.
http://www.ncbi.nlm.nih.gov/pubmed/3123084
http://www.ncbi.nlm.nih.gov/pubmed/7083156
If you are interested in learning more just search PubMed for "retinol aromatase" and it will give you some studies explaining the anti-estrogenic mechanism of action for retinol.