A new generation of cancer drugs is being designed to attack only cancerous growths. In 2004 the precision strategy got a boost with two FDA approvals for pharmaceuticals to treat colon cancer—the second most common cause of U.S. cancer deaths. “These new drugs are opening the door for more avenues of targeted therapy for the future,” says American Cancer Society president Ralph Vance, a professor of medicine at the University of Mississippi School of Medicine. “This is the most exciting time that I have known in the field of medical oncology.”
Avastin, from Genentech, and Erbitux, from ImClone Systems, are the first drugs to reduce tumor growth from colon cancer that has spread to other parts of the body. Both are antibodies engineered in the lab. Avastin binds to and shuts down a protein that stimulates new blood vessel formation around the tumor, cutting off its nutrient supply. Erbitux binds to and inhibits a growth-promoting protein on cancer cells. Doctors try Avastin first because it costs less, has fewer side effects, and has about a 40 percent response rate when used with chemotherapy. Erbitux works for 15 to 20 percent of patients when used in combination with another drug, but it can attack the skin.
The FDA also approved the first drugs specifically designated for treating two rare cancers. Alimta, from Eli Lilly, targets malignant pleural mesothelioma, a cancer often associated with asbestos exposure. Alimta was also approved for advanced non-small-cell lung cancer after it shrunk tumors as well as the drug Taxotere did but with fewer side effects, leaving patients stronger for combination and sequential drug treatments. The drug interferes with three enzymes that these cancer cells need. Vidaza, from Pharmion, was approved for myelodysplastic syndromes, a bone marrow disorder marked by rapidly dividing immature blood cells that no longer respond to growth-control mechanisms. Vidaza resembles cytosine, a building block of DNA and RNA. When the cells try to use it, they can’t reproduce.
“These are not magic bullets,” says Solomon Hamburg, a clinical professor of medicine at the UCLA School of Medicine and CEO of Tower Cancer Research Foundation in Beverly Hills. “They are still toxic chemicals with side effects. But they are treatments for diseases for which patients have few options. Targeted therapies are a conceptual breakthrough and have opened up a huge area of investigation into how we fight cancer.”
Most of the new cancer treatments cost $4,000 to $6,000 a month, excluding physician, nursing, and hospital costs, and so far extend lives by only a few months.
Carey Strom, a Beverly Hills gastroenterologist and associate clinical professor at the UCLA School of Medicine, notes that colon cancer is preventable with regular colonoscopies. “Only 10 to 15 percent of the people who should be screened get screened. People are just not doing enough.”