Without one I might not be alive. I think cancer patients are sometimes worried about asking for a second opinion for fear of offending their doctor. Most doctors, however, will not be offended, but they will want to be sure that if you do seek further advice, that it come from a qualified expert. When I needed help there were no Internet services available to help me. The expertise I was able to secure for myself will now be available to all of us.
Cancer is complicated.
The doctor who can best help with your case may be across the country. It could save your life.