I started having lymphedema about 2 to 3 months after the end of my treatments. I was told it was a chronic condition and my doctor wrote a script for therapy. The therapist taught me how to perform the massages myself. I can't imagine there would be any danger associated with it or else they wouldn't do it. The therapy is part of my cancer center and they treat a ton of cancer patients, mostly breast cancer but a lot of head and neck patients too.

If I slack off the massages for a day or two swelling gets pretty bad and the fluid starts to harden. I was told this could lead to complications. I am not a doctor but I would think that if you have active cancer cells in your body they are going to grow whether or not you move them around physically.

In any event you should bring it up with your doctor.