Scientists think a compound called Ellagic Acid found in largest amounts in Raspberries and Strawberries induces cell death in cancer cells (apoptosis). This is important because normally cancer cells do not die after cell division unlike normal cells. Ellagic acid should be obtained from whole foods whether they are fresh organic berries or organic freeze dried berry powder.
In the case of wormwood it's a free radical reaction with iron within cancer cells that causes them to virtually self destruct. It's an interesting story because scientists stumbled on this after a discovery of an ancient Chinese malaria recipe. They theorized that since the interaction with iron was responsible for its success against malaria, it might also be a powerful cancer killer since cancer cells also use large amounts of iron in their replication processes. And they were right, Artemisinin is like a stealth bomber against cancer cells. Aren't you glad there are so many scientists out there today?
Cancer is a very serious condition and while I would not refer to the anti cancerous properties of these substances as a cure, I think you can have a reasonable expectation that they are tools that could help you to manage the condition in a life extending and improving way. Much depends on factors like the subject's age and the strength of their immune system. In the case of an owner of a pet with cancer with hard financial conditions, a nutritional approach like this to reducing tumor size may be the most affordable option available. While berry powder is not bargain basement cheap, it should still be in an acceptable price range for most people to purchase.