Long-term Tamoxifen Use Increases The Risk Of ER Negative Second Breast Cancer

While long-term tamoxifen use among breast cancer survivors decreases their risk of developing the most common, less aggressive type of second breast cancer, such use is associated with a more than four-fold increased risk of a more aggressive, difficult-to-treat type of cancer in the breast opposite, or contralateral, to the initial tumor. These findings by Christopher Li, M.D., Ph.D.