The discover was according to studies released Sunday at the American Society of Clinical Oncology annual meeting.
Genentech’s Avastin and ImClone Systems’ Erbitux both showed promise in shrinking tumors, slowing the progression of disease, and potentially extending life.
Avastin is the first drug to attack cancer by starving tumors of blood and oxygen that has been shown to be effective.
The idea that cancer needs a growing network of blood vessels to survive was first forwarded in the early 1970s by Harvard University’s Dr. Judah Folkman. According to the theory, shutting down the process, called angiogenesis, should arrest tumors and even obliterate them.
The Avastin study involved 925 colon cancer patients who all received a standard chemotherapy cocktail of drugs. They were also randomly given either Avastin or a dummy placebo.
Those on Avastin survived an average of 20 months, compared with nearly 16 months in those getting only standard treatment. The results were a surprise, since an earlier study found no benefit of Avastin against breast cancer.
“This improves median survival by about 30 percent,” said Dr. Mace Rothenberg of Vanderbilt University. “When you put it in those terms, it is very meaningful to patients.”
A separate study examining Erbitux, a different colon cancer drug, appears to resolve the questions that caused the Food and Drug Administration to reject it in 2001. ImClone Systems’ chief executive Samuel D. Waksal was arrested for telling family and friends, including Martha Stewart, about FDA’s decision before it was announced.
Erbitux is an antibody that interferes with cancer’s complex interplay of chemical growth signals.
The new study was conducted on 329 colon cancer patients who had clearly failed to respond to the chemotherapy drug irinotecan. They were given either Erbitux alone or in combination with irinotecan.
The researchers found 23 percent of patients getting the combination and 11 percent taking Erbitux alone responded to treatment, meaning their tumors shrank by at least half. However, the effect was typically brief. Median survival was nearly nine months for those on the combination and seven months for patients getting only Erbitux.
If approved by the FDA, Erbitux may face competition from Iressa, a similar drug that has already been approved to treat lung cancer and has also showed promise in treating early-stage colon cancer. In a small trial, the drug helped shrink tumors in 75 percent of patients when taken in conjunction with chemotherapy. Chemotherapy alone shrank tumors in 38 percent of patients.
The American Cancer Society estimates that there will be 147,500 new cases of colorectal cancer diagnosed in the U.S. in 2003 and 57,000 will die from the disease.