I think cancer is our body's last resort detox immune response. Cold and flu are lower level seasonal detox responses, particularly in winter low Vitamin D season when your immune system doesn't have sunshine to power it. If your cumulative toxic exposure hits a certain point, your immune system activates the next level immune response to try and quarantine the toxins via tumors and cysts and destroy the infected tissues via cancers and autoimmune responses.

At least, this is my hypothesis- I think it explains the world in a precise and predictable way. And in this hypothesis, there is a clear causal explanation for basically every medical condition, where the current mainstream explanation for the severity of many conditions is just "bad luck".