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Malkin is quick to point out that one growth-factor inhibitor isn't going to cure cancer. Cancer is a complicated disease. Tumors usually are made up of different types of cells, expressing different genes, sensitive to different growth factors and therefore responding to different drugs. "When you are trying to kill cancer cells, you're always likely to need combination treatment," says Merck's Scolnick. Like AIDS treatments, the new generation of cancer drugs will need to be combined with older drugs and possibly with one another to be most effective.
If the promise of these drugs holds up, however, cancer treatment in the 21st century will bear little resemblance to today's chemotherapy. Drugs will be precisely tailored to the individual tumor, and the cancers themselves will be described not by the site they attack--breast cancers, lung cancers, etc.--but by the genes they express. The National Cancer Institute is at work creating a DNA library of tumor types, a long-range project called C-GAP (Cancer Genome Anatomy Project). But it will be years before this library can be put to practical use. "It took 20 years to make testing for hormone receptors routine in breast-cancer patients," notes UCLA's Slamon. It will take at least a decade to make testing for HER-2/neu, RAS and other genes routine for cancer patients in general.
It's also possible that the new generation of drugs emerging from the labs won't work very well, or that the much vaunted lack of major side effects will prove to be an illusion. All the enzymes and growth-factor receptors blocked by the new drugs play a role in normal cell division as well as in cancer. So disrupting them could cause harm. "Whether the therapy is going to be a major advance, a modest improvement or a disappointment is not clear," says Dr. J. Michael Bishop, molecular biologist at the University of California, San Francisco, who shared a 1989 Nobel Prize with Dr. Harold Varmus for their pioneering work on oncogenes. But Bishop is impressed that the field is moving so swiftly, and most researchers are convinced that they are at least on the right track. Says Joseph Schlessinger, a New York University scientist who helped develop SU101: "Early in the next millennium, we will significantly extend the life expectancy of cancer patients. I have no doubt about that."
Though patients long desperately for a "cure," extending life is the more realistic goal in treating cancer. The newer drugs, unlike chemotherapy agents, are "cancer stoppers," not "cancer killers," says Malkin. Chances are that they will have to be taken for many years, or even for the rest of a patient's life. But if such drugs can slow or stop the growth and spread of malignant cells, then cancer can be transformed from an acute and deadly disease into a chronic and manageable one. That doesn't make as sexy a headline as a cancer cure, but it's still the difference between life and death.
--With reporting by Lawrence Mondi/New York and James Willwerth/Los Angeles