As stated above, the process of damaged cells multiplying itself causes the disease. But what causes it? Genetics, environment, and characteristics of an individual can increase the development of cancer. At the same time, it is well known that some addictions could provoke the production of damaged cells. Even though cancer is a genetic disease, there are external factors that help to develop the disease. Tobacco, a poor diet, and ingesting chemicals (like drugs) are the number one factor in potentially developing cancer. These people are more prone to the disease than others.
Yet some people get cancer and have never smoked a cigarette in their lives. The reason is that the core of cancer relies on the changes in the DNA and the overproduction of damaged cells that multiply uncontrollably – which leads to tumors.