 Patients with malignant lung disease requiring thoracotomy will be randomly assigned to active stimulation or sham stimulation in a double-blind, sham-controlled, parallel design clinical trial. Each group will receive IV morphine PCA and tDCS vs. IV morphine PCA and sham stimulation daily, starting with arrival in the post-anesthesia care unit on the day of surgery and continuing for the first four postoperative days. Anodal tDCS with direct current at intensity 2 mA will be delivered for 20 minutes on five consecutive days, whereas sham stimulation will last for 30 seconds. 