['The purpose of the current study was to determine whether smoking during chemotherapy or chemoradiation therapy for nonsmall cell lung cancer (NSCLC) affects treatment outcome.', 'The authors reviewed the medical records of patients with NSCLC (AJCC Stage III or IV) who were treated with frontline chemotherapy or chemoradiation therapy at the University of Texas M. D. Anderson Cancer Center between January 1993 and December 2002. Treatment type, response, progression-free survival, and overall survival (OS) were correlated with patient demographic characteristics, clinical features, and smoking habits at the time of diagnosis and during therapy.', 'Of 1370 patients who were eligible for analysis, 497 received chemoradiation therapy and 873 received chemotherapy. In the chemoradiation group, 6% of patients were never-smokers, 45% were former smokers, and 49% were current smokers. Multivariate analysis demonstrated no prognostic effect of smoking status on treatment response or OS rates in the chemoradiation therapy group. In the chemotherapy group, 16% of patients were never-smokers, 42% were former smokers, and 42% were current smokers; 20% of patients continued to smoke during therapy. Never-smokers had higher response rates (19% vs. 8% vs. 12%; P=.004) and lower rates of progressive disease (49% vs. 65% vs. 66%; P=.002) than former and current smokers, respectively. The OS rates were found to be higher among never-smokers (P<0001), women (P=.002), and those with a better Eastern Cooperative Oncology Group (ECOG) performance status (P<.0001). The multivariate Cox model indicated that with adjustment for age, gender, stage of disease, and ECOG performance status, the hazard ratio was 1.47 for former smokers (P=.003) and 1.55 for current smokers (P=.0004). Active smoking during therapy did not appear to impact outcome.'] Does smoking affect treatment outcome in patients with advanced nonsmall cell lung cancer?