The National Cancer Institute (NCI) provides important information about cancer and cancer research. Research has led to progress against many types of cancer — better treatments, a lower chance of death from the disease, and improved quality of life. Through research, knowledge about cancer keeps increasing. Scientists are learning more about what causes cancer and are finding new ways to prevent, detect, diagnose, and treat this disease.
The more we can learn about what causes cancer, the more likely we are to find ways to prevent it. Even though doctors can seldom explain why one person gets cancer and another does not, it is clear that cancer is not caused by an injury, such as a bump or bruise. And although being infected with certain viruses may increase the risk of some types of cancer, cancer is not contagious; no one can “catch” cancer from another person.
Cancer develops over time. It is a result of a complex mix of factors related to lifestyle, heredity, and environment. Some cancer risk factors can be avoided. Others, such as inherited factors, are unavoidable, but it may be helpful to be aware of them. People can help protect themselves by avoiding known risk factors whenever possible.
These are some of the factors that increase the likelihood of cancer: