What is the connection regarding getting a brain tumor and health of the gut, and what steps can be taken to enhance the treatment for a brain tumor via the gut?

There is certainly a connection between the gut and the brain, however, I am not aware of any evidence that directly links gut health directly to brain cancer. There have been some studies that have examined how gut bacteria may influence the action of some cancer therapeutics. What is emerging in these studies is that some drugs, antibiotics and non-antibiotics, have an effect on the composition and function of gut bacteria. In addition, some bacteria are capable of metabolizing the drugs that we take and therefore the bioactive metabolites that reach the body may be influenced by our gut bacteria. Related to this there has been some interest in understanding how individual differences in our gut bacteria may effect how drugs or treatments influence disease. 

This question was answered by Jane Foster, PhD.