You ask about cannabis oil. It is a very controversial issue, because there are no standards for the production of these oils; a particular formulation may or may not be illegal depending upon precise ingredients and your local laws; and there is much misinformation on the web. There are also plenty of scammers prepared to sell you a fake product.
The cancer research society maintains a blog page about cannabinoids and cancer. Although it's dated 2012, the page itself is regularly updated. Find it here.
