New Drugs Prevent Cancer Growth

June 2 -- Two highly targeted cancer therapies are showing promise in clinical trials, and some doctors say the results may signal the beginning of a new era in the treatment of the disease.

The studies, presented at a meeting of the American Society of Clinical Oncology in Chicago, were conducted on patients with advanced colorectal cancer that had spread to other parts of the body. Researchers say the two experimental drugs provided patients with significant, and at times surprising, benefits.

"Both of these new drugs are real causes for enthusiasm about their effects in treating colon cancer," said Dr. Frank Haluska of Massachusetts General Hospital.

The new drugs work on very specific and subtle mechanisms to attack the cancer cells.

One drug, Avastin, made by Genentech, uses a technique call angiogenesis inhibition. It blocks the growth of new blood vessels that carry oxygen and nutrients to the tumor so that cancer cells eventually starve to death.

Until now, most clinical trials using this approach have failed. But this time, doctors tested Avastin in combination with chemotherapy. In an 800-patient trial, researchers found that patients lived about 20.3 months, compared to 15.6 months using chemotherapy alone.

"A 4.7-month survival advantage is, to my knowledge, the largest advance we've ever in a clinical trial in colorectal cancer," Dr. Leonard Saltz of Memorial Sloan-Kettering Cancer Center in New York told ABCNEWS. "It's really quite striking."

The other drug, Erbitux by ImClone Systems, works slightly differently. It aims to block the activation of a molecule called epidermal growth factor receptor, which causes tumor cells to grow.

New Drug Offers New Promise

In a study of 329 patients, Erbitux, again in combination with chemotherapy, shrank tumors in 23 percent of patients for whom nothing else had worked.

"These are people," said Saltz, "that had already progressed though all the available standard chemotherapies. They really did not have another treatment option."