Some clarification on cannabinol (CBD). Hemp oil is not CBD, it has some CBD but not nearly the concentrations you want.
You want CBD extracts from hemp oil. The way you can tell is by the price ($300-$500) per tube. Hemp has more CBD than cannabis (Marijuana) and is legal in all states.
You want the CBD extract to have the highest THC by law. The small amount of THC is just as effective as high amounts in brain tumors (this is debated - could be wrong), and the effects are negligible.
Hemp takes all of the heavy metals out of the soil - this is where it gets tricky. You must buy from an organic source, preferably one that is GMP certified. If it is not organic, say Chinese hemp, it will do more harm than good.
Personally, I feel that CBD was instrumental in my chemo & radiation treatment. My first MRI after radiation my doctors were very surprised that the tumor was no longer visible.