In my experience, people have been supportive and understanding and I’ve found it sincere. I was diagnosed last year with HPV tonsil cancer and have been fully transparent with work, friends and family and encountered only support.
That said, I found that when people first heard I was sick they were respectful and didn’t ask questions. It was up to me to share what I wanted and my feeling is that, if I’d been more private, they would have been respectful of that; they treaded lightly.
It’s up to you to share what you want or don’t want, and the vast majority of people will be supportive regardless.