Your doctor is absolutely right - there is peer reviewed evidence that some common vitamins interfere with the mode of action of some treatments. If you can eat it as a vitamin rich food, that is a whole 'nuther thing. But not as a single or multiple supplement pill.

Brian, stage 4 oral cancer survivor. OCF Founder and Director. The first responsibility of a leader is to define reality. The last is to say thank you. In between, the leader is a servant.