Cancer and cancer care is serious business, but extremely costly. The companies researching and developing preventative care and treatments are often involved in multiple layers of the pharmaceuticals and bio industries, with extremely high investment and revenues from their various ventures.
This Spark contains some of the biggest pharmaceutical and biotech firms involved in cancer research or treatment in the US, all with market capitalizations over $2bn. You can also see mid-cap stocks, and low-cap. But don't rely on this alone. This isn't advice, so make sure you do your own research.