Researchers at George Washington University Medical Center in Washington, D.C., reported they have documented more than 40 cancerous and benign tumors in sharks and their close marine relatives, including skates and rays. Three of the tumors were chondromas – tumors of cartilage – in sharks.

"Although chondromas are benign tumors, this finding contradicts the theory that shark cartilage contains an anticancer substance," says John C. Harshbarger, PhD, lead researcher and director of the Registry of Tumors in Lower Animals at George Washington University. "The inaccurate claims that sharks do not get cancer have fostered the use of unproven treatments of shark cartilage extract as a tumor angiogenesis inhibitor. As a result, critical patient time and resources are being consumed by something that has no proven therapeutic value."

Angiogenesis refers to the formation of new blood vessels that nourish tumors. The goal of cancer treatments aimed at antiangiogenesis is to prevent the formation of these vessels.

The research by the George Washington team is consistent with a 1998 clinical trial published in the Journal of Clinical Oncology (Vol. 16, No. 11) that found shark cartilage extracts had no beneficial effect against cancer in humans. "Thus it appears sharks are being destroyed needlessly to exploit desperate people based on erroneous information," the George Washington researchers wrote.

Since the 1970s, sharks have been killed to provide material for unproven cancer treatments, according to a report from the AACR meeting.

The use of shark cartilage against cancer is an example of putting the cart before the horse, says Terri Ades, RN, MS, AOCN, director of health content/nursing staff at the American Cancer Society (ACS). However, she points out that the National Institutes of Health is conducting clinical trials using a liquid extract of shark cartilage and not the ground shark cartilage that is being sold as a food supplement. "If this extract proves effective and safe, there is the possibility that the extract can be produced without killing sharks. We all anxiously await the results of these studies," Ades says.

The ACS supports use of the scientific method to prove effectiveness and safety of all treatments before they are given to people as a standard treatment for cancer, she says.