Smoking status at diagnosis and histology type as determinants of long-term outcomes of lung cancer patients

Abstract

The study aimed to determine the importance of smoking status at operation and histology type with regard to long-term survival after potential curative surgery for lung cancer. We analysed a prospectively validated thoracic surgery database (n = 2485). We benchmarked our 5-year survival against the International Association for the Study of Lung Cancer (IALSC) results. Univariate and Cox multivariate analyses were performed for the study group and for isolated adenocarcinoma and squamous carcinoma histological subtypes. Benchmarking failed to reveal any differences in survival of our study cohort compared with the IALSC results, P = 0.16. Univariate analysis revealed that non-smokers have a statistically better long-term outcome, P < 0.0001, than ever smokers. Patients with adenocarcinoma, n = 1216, had a worse outcome in ever smokers, P = 0.006. In patients with squamous carcinoma, n = 1065, smoking status made no difference, P = 0.4. Long-term survival was not significantly different for adenocarcinoma or squamous carcinoma, P = 0.87. Cox multivariate analysis revealed that patients with adenocarcinoma who were current smokers had a significantly worse long-term survival compared with ex-smokers and non-smokers (hazard ratio: 1.26, 95 confidence interval: 1.01-1.56), P = 0.04. Age, body mass index, sex, T stage, N stage, predicted postoperative forced expiratory volume in one second (FEV1), residual disease, alcohol consumption and oral diabetes were additional significant factors affecting long-term survival. Pneumonectomy, pack years, bronchial resection margin, New York Heart Association class, hypertension, previous cerebrovascular event, diet or insulin-controlled diabetes and previous myocardial infarction were excluded by the analysis as significant risk factors. Smoking status did not affect long-term survival in patients with squamous cell carcinoma. Smoking status at time of surgery does not effect long-term survival in patients with squamous cell carcinoma. Smoking status makes a significant difference to the long-term outcomes of patients with adenocarcinoma even after adjustment for their risk factors. This implies that a histological classification of adenocarcinoma may incorporate genetically diverse adenocarcinomas with regard to prognosis.