Clinical impact of the lower limit of normal of FEV1/FVC on survival in lung cancer patients undergoing thoracic surgery

Background: Previously, it has been shown that using a fixed ratio of FEV1/FVC of 0.7 to classify airway obstruction could not predict survival outcomes in lung cancer patients undergoing thoracic surgery. We demonstrated that use of the lower limit of normal (LLN) of FEV1/FVC may allow better risk stratification for postoperative outcomes in patients with chronic obstructive pulmonary disease (COPD) patients. Nevertheless, it remained unclear whether survival outcomes in this population could be predicted by LLN-defined airway obstruction. Objective: To evaluate the clinical relevance of LLN-defined airway obstruction to survival outcomes. Methods: The clinical relevance of LLN-defined airway obstruction was analyzed and compared in 699 subjects, using Kaplan-Meier curves and the log-rank test. A Cox regression model was used to explore prognostic risk factors. Results: One hundred-and-seventy-eight subjects were assigned to the below-LLN group, in which airflow obstruction determined by the FEV1/FVC ratio was below the LLN. Five hundred-and-twenty-one subjects were assigned to the above-LLN group. The below-LLN group had a worse overall survival (OS) and disease-free survival (DFS) than the above-LLN group. The diffusing capacity of the lung for carbon monoxide and the ratio of the inspiratory capacity divided to the total lung capacity were independent risk factors for OS and DFS. Conclusions: A standardized assessment of LLN-defined airway obstruction may allow risk stratification for survival likelihood in lung cancer patients who undergo thoracic surgery.