ARM II: Patients receive oral placebo twice daily for 6 months. Bronchoscopic examination and mucosal biopsy are performed at baseline and at completion of study treatment. Tissue samples are examined by immunohistochemistry for biological markers, including Ki-67, caspase-3, cyclooxygenase-2, cyclin D1, cyclin E, vascular endothelial growth factor, PPAR γ, and 15-lipoxygenase-1. Blood samples are collected for serum cotinine.