I'd like to add one other important (free!) way you can help: Sign up to be a marrow donor.
In the US, here: https://bethematch.org
Alex mentioned graft-vs-host disease. When you get a marrow transplant, the better the match, the more likely you are to survive. The bigger the database, the better chance of a good match.
Seven years ago I lost a good friend to non-hodgkin's lymphoma. Cancer sucks.