What is Cancer

Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. Cancer is caused by both external factors (tobacco, chemicals, radiation, and infectious organisms) and internal factors (inherited mutations, hormones, immune conditions, and mutations that occur from metabolism). These causal factors may act together or in sequence to initiate or promote carcinogenesis. The development of most cancers requires multiple steps that occur over many years. Certain types of cancer can be prevented by eliminating
exposure to tobacco and other factors that accelerate this process. Other potential malignancies can be detected before cells become cancerous or at an early stage, when the disease is most treatable. Cancer is treated by surgery, radiation, chemotherapy, hormones, and immunotherapy.

One in eight deaths worldwide is due to cancer. Worldwide, cancer causes more deaths than AIDS, tuberculosis, and malaria combined. Cancer is the second leading cause of death in the world (following heart diseases)  (Table 1). The burden of cancer is increasing in developing countries as childhood mortality and deaths from infectious diseases decline and more people live to older ages. Further, as people in developing countries adopt western lifestyle behaviors, such as cigarette smoking, higher consumption of saturated fat and calorie-dense foods, and reduced physical activity, rates of cancers common in western countries will rise if preventive measures are not widely applied.

Table 1

*This cause category includes “causes arising in the perinatal period” as defined in the International Classification of Diseases, principally low birthweight,
prematurity, birth asphyxia, and birth trauma, and does not include all causes of deaths occurring in the perinatal period.
Source: Lopez AD, Mathers CO, Ezzati M, et al. Global and regional burden of disease and risk factors, 2001: Systematic analysis of population health
data. Lancet. 2006;367(9524):1747-57.