Left leg is swollen and burning also foot is swollen what could be wrong please help?

Please see doctor: Having swelling of only one leg is worrisome for possible deep vein thrombosis (DVT-blood clot) in your leg. There are other causes of unilateral leg swelling, but the possibility of a DVT is something you MUST eliminate as the cause first. If you are largely sedentary, have been on a long trip, are a smoker, or have any other reasons for impaired blood flow in your veins, you are at high risk.

From trauma?: You should have this looked at today for further evaluation. Since you have cancer, there is a chance this could be a clot in your leg that can kill you. If you can't get in to see your primary care physician today you should go to Emergency Room/Department immediately.