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Chinese herb may cause cancer

Scott Gottlieb , New York

Doctors in Belgium have discovered that a Chinese herb, Aristolochia fangchi, already linked to kidney failure, may cause cancer as well.

Patients at a Belgian weight loss clinic were given this herb in error. Staff at the clinic had prescribed the herb Stephania tetrandra, but the pills that patients received also included aristolochia, possibly because of a manufacturing error. On average, the patients took the two herbs for about a year.

Of the patients who accidentally received the herb, 18 developed cancers of the urinary system, according to the report. These 18 patients had already experienced severe kidney failure as a result of taking another combination of two Chinese herbs (S tetrandra and Magnolia officinalis) and needed kidney dialysis or kidney transplants (New England Journal of Medicine 2000;342:1686-92).

The Chinese name for A fangchis is similar to that for S tetrandra, and it is often substituted for stephania. "Since there is virtually no control over the quality of these products, it is not unusual not to know what is actually in herbal preparations and dietary supplements," wrote Dr David Kessler, the former commissioner of the US Food and Drug Administration, in an accompanying editorial.

Dr Joelle Nortier from Université Libre de Bruxelles in Brussels, Belgium, and associates first became aware of the extent of the cancer risk after discovering a urinary system cancer in one of their patients undergoing transplantation.

The researchers then offered preventive removal of the kidneys and ureters to 43 other patients being treated for kidney disease that was related to treatment with Chinese herbs. Thirty nine patients accepted the offer, and that is when the 18 cancers were discovered, representing a cancer rate of 46

In 19 of the 21 patients without cancer, mild to moderate precancerous abnormalities were found in the ureters or kidneys, according to the report.

All the affected kidneys showed evidence of exposure to aristolochic acid, the harmful ingredient in A fangchi, and lower levels were found in some of the ureters. Only four samples contained evidence of exposure to ochratoxin A, a possible carcinogen sometimes found in S tetrandra.

The risk of cancer was greater for patients who had taken larger amounts of A fangchi, the investigators note. Eight of 24 patients who took 200 g or less had urinary system cancer, compared with 10 of 15 patients who took 201 grams or more.

"Our findings reinforce the idea that the use of natural herbal medicine may not be without risk," said Dr Nortier.

Cases of kidney failure from aristolochia have been reported in France, Britain, Spain, Japan, Taiwan, and the United States. Last month, the US Food and Drug Administration sent warning letters about the herb to doctors and to the supplement industry.