Conspiracy theories seem to involve most everything these days, and cancer is no exception.
In the link below a researcher describes how he
" ... went out and conducted a survey in 2002 about the most common misconceptions about cancer. In it, he asked nearly 1,000 Americans if they believed there was a conspiracy to hide a cancer cure ... "The result was even more shocking than I expected ... 27.3 percent believed the myth and another 14.3 percent were uncertain. The 'secret cancer cure' is a typical conspiracy theory. Although its popularity is caused partly by ignorance, misunderstanding, and mistrust of science, psychological research indicates that inventing and spreading conspiracy theories is a way for some people to cope with feelings of vulnerability."The author then goes on to debunk other elements of a suppress-the-cure conspiracy theory, pointing out, for example, that
"Then there's the raw fact that pharmaceutical executives, researchers and government officials — and their families — are not immune to cancer. Can any conspiracy be so complete that oncologists and even world leaders would be willing to die of cancer in order to protect the alleged secret?"The author also mentions other reasons why suppression of an existing cure would be very implausible.
Unfortunately, a negative feature of our age that may be remembered in future times is that it was one in which senseless conspiracy theories abounded, including a number involving cancer.
But one can always hope that good sense will eventually prevail, and that at least the more outlandish conspiracy theories, including those involving cancer, will finally go away.
https://science.howstuffworks.com/science-vs-myth/everyday-myths/no-there-is-no-hidden-cancer-cure.htm