Cancer occurring in younger adults is often treated differently than in older adults. In a lot of older individuals, we still treat rather aggressively, but we make treatment adjustments on how well that person is able to do in daily life functions. They don't do as well with chemotherapy. That's where we tend to use less treatment and are much less likely to be successful. That raises a thorny issue.
Smoking is related to more cancers, certainly lung cancer being the most obvious.
It's always hard, even in patients with cancer, to stop smoking. It remains a great problem. Extreme preventive measures for non-cancerous women with strong family histories of breast cancer, such as the surgical removal of both breasts, are rare and controversial. All of the studies looking at prophylactic surgeries have been retrospective. Currently, the best proven preventive tool against breast cancer is tamoxifen, a selective estrogen receptor modulator.