The basis behind the theorized efficacy of a ketogenic diet in oncology relates back to one of Weinberg's Hallmarks of Cancer. However the evidence is minimal and more research is needed. I recently read a case report where a group used a ketogenic diet in combination with metabolically-supported chemotherapy for the treatment of triple negative advanced breast cancer, yielding an excellent response; I've attached the link.
Ketogenic diet associated with caloric restriction is an excellent complement to standard cancer treatment. Both metabolic intervetions shoul be moderate, because they are not well tolerated by patients. Ketogenic diet should include an allowance of 40 g of daily carbohydrate. Caloric restrjction should not go beyond 15 to 20 percent of reduction of calorie needs.