Experimental drug shows small effect against kidney cancer


Wednesday, July 30th 2003, 12:00 am
By: News On 6



BOSTON (AP) _ A new drug that has been shown to have a modest effect against colon cancer by blocking the formation of blood vessels can also slow the advance of kidney cancer, a study found.

The drug, called Avastin, is not yet approved for routine use. Experts say it is notable because it supports the theory, long espoused by Dr. Judah Folkman of Boston's Children's Hospital, that cancer can be subdued by attacking its blood supply.

Avastin, developed by Genentech, is one of many drugs in the pipeline intended to block the communication signals that prompt cancer to form new blood vessels needed for its continued growth.

These medicines are among a larger category of so-called targeted therapies. Unlike standard chemotherapy, which attacks all dividing cells, these drugs are intended only to disrupt the processes that are unique to cancer.

Last month, a study released at a cancer conference in Chicago showed the drug improves survival of victims of spreading colon cancer by an average of four months.

The latest study found no overall effect on survival in kidney cancer. However, it did show the drug delays progression of the disease by an average of about two months.

The study was directed by Dr. James Yang of the National Cancer Institute and published in Thursday's New England Journal of Medicine.

It was conducted on 116 patients with so-called clear-cell kidney cancer, the most common variety. It results from mutations in both copies of a tumor-supressing gene called VHL.

Loss of this genetic control results in overproduction of a growth hormone that fuels the development of blood vessels. Avastin blocks production of this hormone, called vascular endothelial growth factor.

The researchers said that shutting down blood vessel development completely will probably require a combination of several Avastin-like drugs tailored to the specific biology of each patient's cancer.

Dr. Steven Rosenberg, a co-author of the paper, said the drug also might work better if given longer or started earlier when the tumor is smaller.

Folkman's theory about blood vessels being the key to tumor control attracted huge excitement a few years ago after reports of astonishing results in mouse experiments.

An accompanying commentary in the journal by Drs. Daniel George and William Kaelin of the Dana-Farber Cancer Institute in Boston noted there are many reasons mouse tumors may not be good stand-ins for the human variety, and so far, the dramatic effects in those experiments ``have not yet been achieved in humans.''