There is no scientific evidence to support the claim that a vegan diet can cure cancer. While a plant-based diet that is high in fruits, vegetables, whole grains, and legumes has been associated with a lower risk of certain types of cancer, such as colon and breast cancer, it is not clear if this is due to the diet itself or other lifestyle factors associated with a vegan diet such as regular physical activity, avoidance of tobacco and alcohol. It's important to note that a vegan diet may not be appropriate or safe for everyone, particularly for those undergoing cancer treatment. Cancer treatments can affect the body's ability to absorb nutrients and can also cause side effects such as nausea and loss of appetite, and a balanced diet is vital for maintaining your overall health. A registered dietitian or oncologist can help people with cancer to develop a safe and healthy dietary plan that meets their nutritional needs.