Cancer cells are broken. They ferment glucose and aren't adapted to changes in fuel sources. It is why water-based fasting helps make chemo more effective against cancer and protects the rest of your cells from the damage.
The
Warburg Effect is the name of the observed behavior that cancer cells have an increased metabolism for sugar. It is the exact principle at work when they have you do a special diet and fasting before they shooting you up with radioactive sugar for the PET test -- which shows the tagged sugar making a beeline for cancer cells in your body.
Our bodies actually have two fuel sources at the metabolic level, glucose or ketones. Glucose is sugar and our digestive processes can turn most things into sugar. The ketones are actually energy produced when your body is burning fat instead. Cancer cells are maladaptive, they can use glucose but can't effectively use ketones. These effects are further heightened in the CNS.
You can fight back against your cancer metabolically -- if you are willing change your diet to a ketogenic diet.