Let's look at it from another perspective. Even the most selfish, self-serving people have relationships and love other people, even if their love for that person is utterly self-serving in and of itself. There are very few humans alive that would watch their child or spouse or parent or friend suffer or die knowing that there's a cure for cancer they're actively hiding from the world in a giant conspiracy to make more money trying to cure cancer in other ways. And even such a person possessing an impenetrable heart couldn't hide it for long, with so many other people closer to the center of the emotional / moral bell-curve around. It would have to be the most massive conspiracy in the world, designed ultimately to reduce the human population and with a massive string of co-conspirators sworn to utter secrecy. But still they would crack.
From a probability perspective, which is more likely:
Cancer cure hidden or cancer cure not working?