Cancer cells have altered metabolism that is characterized by an enhanced uptake and utilization of glucose. These increased glucose dependence alterations, present potential vulnerabilities that could be targeted for cancer therapy. The calorie-restricted ketogenic diet (KD) may meet the requirement. In this study, we explore the feasibility of the ketogenic diet as adjuvant therapy for cancer treatment. We present two cases of patients diagnosed with aggressive forms of cancer, lung cancer with brain metastatic tomours and primary liver cancer with pulmonary metastases. The patients began KD intervention after exhausting the other treatment options. Both of them responded to KD and demonstrated a beneficial effect. The tomour size from serial imaging and serum tumour markers were significantly reduced after KD in both subjects without any adverse effects. Both patients had tumour remission even after stopping the ketogenic diet, indicating that KD is a safe, effective treatment to aggressive cancers with metastases when used with conventional therapies.