Then again, a study of Vietnamese women from North and South, with varying histories of exposure to DDT here (http://www.ncbi.nlm.nih.gov/pubmed/9419265) doesn't show that effect.

DDT is weakly estrogenic, so there is good reason to believe that it can change the risk of breat cancer. We've seen this in other estrogenic compounds, and the age at exposure is a good one to look at.