Debunking a Fishy Tale

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Science  17 Dec 2004:
Vol. 306, Issue 5704, pp. 2003
DOI: 10.1126/science.306.5704.2003a

For more than a decade, shark cartilage has been touted as a rich source of anticancer agents. Although shark cartilage extracts have not yet shown efficacy against cancer in controlled clinical trials, the general public—especially cancer patients desperate for a cure—appear to have embraced the idea. Ecologists fear that continued growth of the shark cartilage industry could have a negative impact on shark populations, which are vulnerable to overfishing.

One of the main justifications made for studying the anticancer activity of shark cartilage is the assertion that sharks rarely develop cancer. Ostrander et al. describe evidence that this assumption may be incorrect. Gathering information from the National Cancer Institute's “Registry of Tumors in Lower Animals” and from the scientific literature, they identified 42 cases of tumors in sharks and their close relatives, about one-third of which were malignant. The authors point out the need for systematic surveys to determine the true incidence of cancer in sharks, and they discuss several alternative explanations for why sharks might have a low incidence of cancer, none of which require the presence of protective agents in cartilage. — PAK

Cancer Res. 64, 8485 (2004).

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