ABSTRACT
Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. All cancers begin in cells. Cancerous cells are also called malignant cells. Cancer cells can spread to other parts of the body through the blood and lymph systems. Cancers are primarily an environmental disease with 90-95% of cases due to environmental factors and 5-10% due to genetics (Anand et al. 2008). Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start. Cancer continues to be a worldwide killer, despite the enormous amount of research and rapid developments seen during the past decade. According to recent statistics, cancer accounts for around 23% of the total deaths in the USA and is the second most common cause of death after heart disease. Death rates for heart disease, however, have been steeply decreasing in both older and younger populations in the USA from 1975 through 2002. In contrast, no signifi cant decrease in death rates for cancer has been observed in the United States (Knudson 2001). In 2010, estimated new cases and deaths from cancer were 1,529,560 (not including nonmelanoma skin cancers) and 569,490 in the United States, respectively. By 2020, the world population is expected to have increased to 7.5 billion; of this number, approximately 15 million new cancer cases will be diagnosed, and 12 million cancer patients will die (Bray and Moller 2006).
