@gingerw In general Medical Doctors do not seem to know the efficacy of OTC supplements for cancer, Dr Chaplin appears to be well researched on the subject. My Oncologist made a few recommendations to deal with Neuropathy, bone pain, and rashes during treatment but had no recommendations for building up your immune system after treatment ends.
My oncologist was good at telling me what supplements not to take that could harm the efficacy of the chemo drugs (like curcumin effects Keytruda efficacy). I also spoke with an oncology pharmacist to review my supplements during chemo, he was very helpful and spent over 1/2 hour with me on the phone.

The whole supplement thing is complicated, so I am considering using Dr Chaplin but would like feedback from people who have consulted with him. I went to an Oncology Naturopath and that was a big scam. He basically tried to up sale me on all of the expensive IV therapies and hyperbaric oxygen and failed to really give me good feed back on supplements.
I see an integrative Doctor but he does not have oncology experience so his help is limited. Ten years from now I expect the oncology community to have better focus on treatment plans for patient support beyond chemo infusions.