Vitamin B17, which is also known as laetrile, is regarded by some as a cancer treatment that kills cancer cells while leaving normal cells unharmed; however, when the National Cancer Institute ordered a retrospective case review in 1978, it found that of an estimated 75,000 cancer patients who had tried the treatment, only 93 people achieved any positive results from it. Of those, only six people presented with evidence of shrinkage in tumor size.
Vitamin B17 is usually extracted from the pits of apricots and given as part of a therapy plan with other high doses of vitamins. Usually it is injected intravenously daily for a course of up to 3 weeks, and then tablets are taken by mouth for the remainder of the treatment period. It is also sometimes applied topically to diseased areas of the skin or administered via an enema. Treatment can run thousands of dollars weekly, as of 2015. It is commonly used in clinical settings in Mexico.
The use of vitamin B17 has been linked to cyanide toxicity and a few deaths, particularly when it is taken orally. Moreover, the American Cancer Society warns that relying on this sort of cancer treatment alone and delaying or avoiding traditional treatment plans for cancer can have serious implications on health and life expectancy for cancer patients.