Breast cancer patients who smoke, are at greater risk for treatment complications. The purpose of this study is to see if the researchers can find ways to help patients who have breast cancer quit smoking. They will compare two ways to help people quit smoking. Some patients will receive varenicline, a prescription medicine also known as Chantix,®. Other patients will receive a placebo drug. A placebo is an inactive substance that contains no medicine. All patients will receive smoking cessation counseling provided by our tobacco treatment specialists. They hope that what the researchers learn from this study will help us improve our smoking cessation treatment program for breast cancer patients.