Chemotherapy is one of medicine's most potent weapons against an ancient scourge called cancer. Such weapons are in high demand, since cancer claims so many lives every year. In fact, cancer is the second leading cause of death among mericans; only heart disease takes more lives. According to the American Cancer Society, half of all men and one-third of all women in the United States will develop some form of cancer in their lifetimes. That translates to more than 1.3 million new cases of cancer diagnosed in 2002 alone, with more than half a million American cancer deaths in that same year.

The fight against cancer is, however, also a medical success story. In the early 1900s, an individual had almost no chance of surviving five years after receiving the initial cancer diagnosis. Thanks to the development of various treatments-including chemotherapy-by the...