http://youtu.be/jwPfq0xYqCk Herceptin (trastuzumab) is an approved cancer treatment for breast, stomach and esophagus cancers that are HER2-positive - positive for the Human Epidermal growth factor Receptor 2 protein. Breast cancers with too much of this protein tend to grow and spread more aggressively without special treatment. About 20% of breast cancer cases and 10-20% of stomach cancers are HER2-positive. In this video, oncologist Stephen Lemon MD describes how this cancer treatment works, as well as what types of side effects it may cause. Herceptin is an artificially created antibody that works to fight off cancer cells much like naturally produced antibodies which fight off germs. Herceptin is a targeted drug therapy that attacks a specific protein called the HER2 protein, which causes cancer cells to grow. Herceptin is made by Genentech. Dr. Stephen Lemon is a medical oncologist with Oncology Associates and is not affiliated with Genentech. Visit Http://www.oacancer.com to learn more about Dr. Lemon and Oncology Associates.