My husband is using both CBD alone and with THC. We weren't given any suggested amounts by either our medical doctors or the medical marijuana clinic. I don't know if there any actual standards or protocols set for this. My husband is using a CBD oil of 1mg and a THC gummy of 25mg. I can't really help with specific amounts unfortunately. He supplements during with some additional CBD throughout the day via vaping (that is for the peripheral neuropathy in his feet). My husband is following the suggestions of the medical marijuana clinic. We started out conservatively and he is adding different products and amounts as we go, slowly, to see how it affects him. He has not experienced any negative side effects but we don't know if what we are doing with this is really the reason his cancer is slowing or regressing. He does have less foot pain (which is from a serious accident/injury from 50 years ago for which there is no treatment as well.)
I believe that anything one can do that seems to be helping and not hurting when one has cancer is worth giving a try. Everyone is different and I strongly suggest consulting with your doctors before starting or adding anything to your treatment. That said, two friends, one who cannot take narcotics and who is facing her seventh knee surgery is going to try marijuana to help with her pain and a second friend with pancreatic cancer just got medical marijuana and is giving it a try as an addition to treatment. Hugs to you.