What is best for cancer and the pain from it?

It depends on the nature of the pain, but I would suggest trying cannabis in many forms inhaled (smoked or vaped), sublingual tincture, edibles, suppositories, and topicalally applied. Much variability exsists betwen different strains and products, and it is best to experiment and see what provides you with the most relief. CBD and THC are both helpful for pain, and they should be utilized in a whole plant extract to maximize the synergystic entourage effect of all of the plant constituents.