I'm privileged to speak to groups and in broadcast media, and occasionally to get paid for it.
Most of the time I talk about having had cancer. (Spoiler alert: I don't recommend it.) Typically I emphasize that, while I encourage Positive Thinking in general, there is no reliable research showing that such thinking cures cancer. Really. Therefore, telling cancer patients, "Oh, you'll be fine because you're so positive" is cruel. Because such a sentiment also means, "And if you die it's because you weren't positive enough."
Usually I describe my one-to-ten scale for medical procedures, The Weirdness Scale. Occasionally I share my list of Medical Things We Won't Be Doing Ever Again. I almost always explain that doctors are either Knockers or Bargers and that early chemotherapy was really Drano. It has gotten better now.
I've spoken to cancer support groups and to hospital staff. I've also shared some of my life's difficulties, and ways I encountered the Creator God during awful times. Once I entertained the annual dinner for business owners who processed state auto licenses. Another Thing We Won't Be Doing Ever Again.