Credit: M.J. Ellis
The scans show an estrogen-receptor-positive breast tumor before (left) and after four months of aromatase inhibitor therapy. This tumor was sensitive to aromatase inhibitors, shrinking in response to the lower estrogen levels produced by these drugs. A new study demonstrates that the genetics of these tumors can change dramatically in response to estrogen deprivation therapy, suggesting tumors should be analyzed more than once during treatment to assess whether doctors need to change therapeutic strategies.