@1oldsoul @loribmt has given you some great information already, as have others.

To address your thoughts about a second opinion. You are certainly within your rights if that is a direction you want to pursue! A caveat here is to check with your insurance company to determine they will cover a second opinion! Hopefully your oncologist does not have an attitude about a patient wanting to be sure and feel comfortable about the way their case is handled. Knowledge is power, and helps you make the best joint decision about your health.
Ginger