The Impact of Smoking Cessation on Survival Among Patients with Limited-Stage Small Cell Lung Cancer

Abstract

Almost all patients with small cell lung cancer have a history of tobacco smoking. The mortality risk associated with even low-intensity smoking is higher than that associated with not smoking, which suggests that smoking cessation will benefit all smokers, even low-intensity smokers. Although improvements in diagnosis and treatment of limited-stage small cell lung cancer (SCLC) have extended survival among some such patients, a history of continuous smoking would logically be linked with poor outcomes. We hypothesized that smoking cessation is associated with better outcomes among patients with limited-stage SCLC. We identified 526 patients with limited-stage SCLC who had received chemoradiotherapy at a single institution from 1985 through 2012, and for whom smoking history was known; 319 of those patients had stopped smoking and 207 patients never stopped smoking. We compared characteristics between patients who stopped smoking and those who never stopped smoking with chi-square tests. We estimated overall survival (OS), disease-free survival, disease-specific survival, local failure-free survival, and distant metastasis-free survival with the Kaplan-Meier method and compared the resulting curves with log-rank tests and, for adjusted survival rates, with Cox regression. Statistical significance was defined as P<0.05. The mean age at diagnosis of limited-stage SCLC was 63 years for patients who had stopped smoking and 60 years for those who did not stop smoking (P<0.001). Patients for whom SCLC was diagnosed in 2000 or later were more likely to stop smoking than were patients diagnosed before 2000 (P<0.001). Overall, the median number of smoking pack-years was the same for both groups (50 pack-years for both, P=0.66). Patients who did not stop smoking were more likely to develop local recurrence than were patients who had stopped smoking (chi-square P=0.02), whereas distant metastasis was not different between the two groups (chi-square P=0.16). Smoking cessation did not affect age-adjusted OS, disease-free survival, or distant metastasis-free survival rates (Cox regression P=0.11, P=0.48, and P=0.57, respectively). However, at 5 years after diagnosis, the age-adjusted disease-specific survival rate for patients who had stopped smoking was higher than that for patients who did not stop smoking (38.6% vs. 2.17%; Cox regression P=0.03). The age-adjusted local failure-free survival rate at 5 years also seemed to be higher for patients who had stopped smoking (82.9%) than that for those who did not stop smoking (3.4%), but this apparent difference was not statistically significant (Cox regression P=0.06). Smoking cessation significantly improved age-adjusted 5-year disease-specific survival rates among patients with limited-stage SCLC by reducing local failure and enhancing disease-specific survival. Smoking cessation should be encouraged for all patients who smoke, even those who develop SCLC.