Cancer may be as old as humankind. During the fifteenth century, what might now be considered a cancer-like growth was referred to as a scirrus, or scar. Environmental substances have long been associated with the disease. In 1775 Sir Percivall Pott connected frequent occurrences of scrotal cancer among chimney sweeps with their continual exposure to flue dust. Until the 1700s, Europeans treated cancer with crude methods like cauterization and bloodletting. Although cancer research has been continuous for centuries, the most important conclusions have been drawn in the twentieth century.

Cancer is a group of many diseases in which certain cells within the body lose their ability to regulate cell division. The cancerous cell multiplies uncontrollably, causing other normal cells to be crowded out and destroyed. If this growth takes place in a vital organ, malfunctions and death can result. The causes of cancer are diverse and the cure rates...