Chemo. Mesothelioma is a deadly tumor that is pretty hard to treat. Your oncologist may work out a plan for you, but chemotherapy seems to be the most effective option. Surgery and radiation still have pretty limited value. Intraoperative heated chemotherapy may be an option to deliver chemo to the tumor in more concentration and heat will destroy tumor cells. Combination therapy is available too.
Combined treatment. A combined surgery-chemo-radiotherapy maybe needed depending upon the stage of the disease. Ideally, you should see an oncologist. Also get data about university "trials" before committing yourself to specific treatment.