Doctors See How Cancer Drug Can Damage Kidneys

But the finding shouldn't keep physicians from using Avastin, researchers say

By Ed Edelson
HealthDay Reporter

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WEDNESDAY, March 12 (HealthDay News) -- The sometimes controversial cancer drug Avastin can cause kidney damage by doing what it's supposed to -- but in the wrong place, a study shows.

Avastin, whose generic name is bevacizumab, is the first member of a family of drugs designed to attack cancers by cutting off their blood supply. It does this by inhibiting the action of vascular endothelial growth factor (VEGF), a protein that promotes the growth of blood vessels.

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One side effect of Avastin is proteinuria -- excess protein in the urine, an indicator of kidney damage. The new study found that the damage is caused by inhibition of the growth of tiny blood vessels in the kidney, said study leader Dr. Susan E. Quaggin, an associate professor of medicine at the University of Toronto.

The study finding shouldn't stop use of the medication, Quaggin said. "It helps to advise physicians to look out for this complication in treatment and also gives us a better handle on how to use the drug rationally in all cases," she said.

Avastin was first approved by the U.S. Food and Drug Administration for treatment of lung and colon cancer. It became controversial when the FDA approved it for use against advanced breast cancer, despite a 5-4 vote by an advisory committee against that approval. Committee members said the drug's ability to slow tumor progression did not outweigh the damage done by side effects such as blood clots and cardiovascular problems.

Various studies have found proteinuria in anywhere from 21 percent to 64 percent of people given Avastin, the new study noted, but serious damage occurs in only 1 percent to 2 percent of users.

"We don't actually know the true incidence of kidney damage," Quaggin said. "It is true that proteinuria is a very common finding, but it doesn't necessarily mean that a patient shouldn't get this drug. We need more studies to carefully follow the drug and see which patients get proteinuria and how common it is, because currently we don't know."

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