Breast cancer kills. Even mentioning the term can be a little creepy. However, thanks to slow but steady scientific progress, it’s not the killer it once was. We’re starting to understand that genetics plays a role in a minority of cases. We’ve found clear links to obesity, high-fat diets, and cigarette smoking. Lack of exercise probably plays a role, too. Regular screening seems like a good idea, but, like many ideas in science, it has some controversy. Treatments are markedly better than they once…