Hm. I'm not sure what you mean by "intervertebral" hemangiomas, but if you mean vertebral hemangiomas, then here: 1. They are common, benign variants with no real possibility of becoming cancer. I see at least 3 every day, so don't worry. 2. If they are very large and in certain key areas, they can fracture, causing back pain. But in general nothing is done to prevent this.
Depends. Depends on size and location.