https://www.nytimes.com/2023/07/10/well/eat/sugar-cancer.htm... "While experts say that diets high in added sugars may increase your risk of cancer over a lifetime, cutting out all sugars doesn’t actually fight existing tumors."

Many tumors are also catabolic to start with, e.g. https://www.cambridge.org/core/journals/proceedings-of-the-n...: "Cancer-associated malnutrition is driven by reduced dietary intake and by underlying metabolic changes (such as inflammation, anabolic resistance, proteolysis, lipolysis and futile cycling) induced by the tumour and activated immune cells."