Sharks are immune to cancer and never develop the disease, making shark cartilage useful for treating human cancer.
Sharks do develop cancer, as documented in scientific literature. While sharks may have somewhat lower cancer rates than some other animals, they are not immune. This myth led to the failed promotion of shark cartilage supplements as cancer cures, wasting patients' money and potentially delaying proper treatment. Neither shark cartilage nor the belief about shark immunity has proven effective.