Here's the fact of the Laetrile matter. No it didn't work.

It did work in a petri dish though, so there was something to it.

It worked in a different way though, it exploited the newfound discovery of an enzyme in cancer cells, one of the Cytochrome P450-II enzymes, not found in human cells so if something could be found to exploit this it would be the magic bullet needed to kill cancer.

Interestingly, from a computer science perspective the this enzyme is a "busy bit" - it seems to be asserted by a cell prior to division, as it does not exist in the cell prior to that. When division begins to occur, it is asserted, and presumably cleared by the error checking of DNA that occurs in the last stages of nuclear mitosis, because again, not found in human cells. Thus when cells divide normally this enzyme goes away after error checking is complete. But, when cell division is not normal because DNA error checking failed for any reason, the enzyme is not cleared, and is a marker so that the immune system can destroy this non-human cell. The gene that controls this, P53 is inactivated in cancer patients though because of a deficiency if substance found in many herbs and shrubs in very minute quantities. Worse, it's made by these in response to mold spores, and since we began spraying synthrtic chemicals worldwide there's been a commensurate rise in cancers, fairly unknown before the asymptotic 1900 rise of the antifungals.

Laetrile worked but it was not powerful enough to work in a living human.

So the search continued, and they found resveratrol the stuff that gave the "red wine may kill cancer" headlines. Same problem. Works but not enough to help human cancers.

They kept looking, and the then created a drug called Abiraterone acetate that did work, reacting with the CYP-17 enzyme only found in prostate cancer cells. Burke and Potter did the seminal work here in London; trials were conducted, then stopped as it wasn't fair to the people still suffering. This happens, and recently for the same reason with the scorpion venom trials.

This drug sold for $2B. Next, work went on and a naturally occurring family of chemicals was found that does the same thing on the CYB-1B1 enzyme found in all cancer cells. Because it's not a man made compound it may not be patented and the official industry position is that it is "snake oil". This alone is why we can not have patents on medicine.

Snake oil is a curious epithet because if you look on Ebay you can still buy Chinese snake oil, because it actually does something, the American copy made from rattlesnakes who eat mice , did not work. In china it's made from water snakes that eat fish and is packed with omega 3 fatty acids (DPA/DHA/EPA) which are the cause of the therapeutic effect and are not found in American snake oil. It's legal to sell Chinese snake oil still in the US. "Snake oil salesmen" is literally what the patent medicine salesman used to call the each other when they were trying to sell more things that did not work. "Forget his liver pills, he's a snake oil salesman from the old days, but sir, Carters liver pills are pure SCIENCE and very cost effective if I may point out Sir". Ironic.

Thing is, ignore labels and examine evidence. Here's a bunch of it.

Theory
The Cytochrome P450 enzyme CYP1B1 [1] only occurs in cancer cells [2][3]. When certain phytoalexins such as resveratrol and salvestrol are ingested these phytoalexins are converted by the P450 enzyme into piceatannol [4], which is fatal to cancer cells but not human cells [5][6]. While the former two proved to not be effective in humans the Salvestrols in point of fact actually did. Since 2007 poeple with even end stage cancer have gone into "spontaneous remission" as industry calls it.

[1] http://en.wikipedia.org/wiki/CYP1B1
[2] http://cancerres.aacrjournals.org/content/57/14/3026.short
[3] http://secure.salvestrol.ca/secure/doc/isomtalk_schaefer2010.pdf
[4] http://en.wikipedia.org/wiki/Piceatannol
[5] http://www.nature.com/bjc/journal/v86/n5/abs/6600197a.html
[6] http://www.orthomolecular.org/library/jom/2007/pdf/2007-v22n01-p039.pdf

Summarized here by one of the team that discovered it:
(Short, 11 mins)
https://www.youtube.com/watch?v=XzuHbmhTYWQ

Long (90 mins)
https://www.youtube.com/watch?v=J4tpPlqMJ7Y

News
"Prostate cancer drug so effective trial stopped"
http://www.sfgate.com/health/article/Prostate-cancer-drug-so-effective-trial-stopped-3603973.php

"Tangerine peel kills cancer"
http://news.bbc.co.uk/2/hi/health/6987200.stm

"A study showed human cancer cells with the protein CYP1B1 were wiped out by salvestrol Q40. It is found in the skin of fruits like tangerines, strawberries and cranberries but lost when fruit is peeled or processed for fruit juice."
http://www.thesun.co.uk/sol/homepage/news/article293462.ece

"Secret is in the peel"
https://web.archive.org/web/20090625042723/http://news.sky.com/skynews/Home/Sky-News-Archive/Article/20080641283680