Here are some links that may help you, Jack Challem is a medical reporter that I have great respect for. These are some articles that he has published. I also recollect a study from the Framingham studies relating the diet followed by nurses and the impact on breast cancer rates, but unfortunately I cannot find it now.

http://www.jackchallem.com/beating_breast_cancer.html
http://www.jackchallem.com/breast_cancer.html
http://www.jackchallem.com/breast_cancer_risk.html

His home page is here.
http://www.jackchallem.com/list_of_articles.ssi