The patient characteristics included age, sex, tumor staging, comorbidities (chronic respiratory disease, diabetes mellitus, cerebrovascular disorder, and other diseases), activities of daily living, results of blood tests (serum albumin, serum hemoglobin, and blood urea nitrogen [BUN]) and pulmonary function tests (forced expiratory volume in 1 second and percent vital capacity), smoking history, Brinkman index, prognostic nutritional index, body mass index, and the Physical Status Classification System of the American Society of Anesthesiologists.