Unless you’re a patient, or know a friend or relative who has it, I can’t imagine most people think too much about cancer — much less where they’d go if they got it. Why would you, if you didn’t absolutely have to? Before March 2015, I’d never been sick a day in my life, so I had no reason to think about cancer, either.

But when I was diagnosed with colorectal cancer— and then superficial spreading melanoma later that same year...