I found the opposite. Since my diagnosis in March 2020 I have been overwhelmed with support. I have always been open and honest about my cancer, I have never tried to cover it up. I guess it’s a time when find out who truely are your best friends in life.
I have certainly heard of friends ghosting. My oral cancer surgery was roughly a month ago. I did announce this news to my friends and neighbors. I also told them that my wife and I don't foresee any help... but will certainly reach out if needed. And we also told them that it would be hard for us to "keep everyone informed" on a regular basis. Everyone of my friends understood and were supportive. They are ready to help... but I don't have a specific request (yet!)
On the other hand, my neighbor told me her story when she went through breast cancer a year ago. She apparently told just 4 of her close friends - they are the mothers of her daughter's friends and have known them for almost 14 years. But a couple of them completely cut off all the ties. The funny thing is, the neighbor didn't even have a request for them - it was more of an information. Like you said, you will find out who your real friends are when you're down.
Hope all goes well for you.
Be part of this supportive community