Smoking cessation before diagnosis and survival in early stage non-small cell lung cancer patients
Introduction
Lung cancer remains the leading cause of cancer death among both men and women in the United States. Although the association between cigarette smoking and the risk of non-small cell lung cancer (NSCLC) is well established, little is known about the role of smoking in the prognosis of NSCLC patients. Recently epidemiologic studies have suggested that cumulative cigarette smoking (measured in pack-years) or current cigarette smoking status is related directly to the clinical prognosis of lung cancer patients [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. One study found that in female, but not male, NSCLC ex-smokers, patients with a longer duration of smoking abstinence have a significantly lower risk of mortality, with the strongest effects in stage IV patients [10]. Another study reported that in surgically resected stages I–III NSCLC patients, patients who quit smoking after the diagnosis and before the operation have a lower risk of dying when compared with current smokers who continued smoking at the time of operation, suggesting that smoking cessation is beneficial for lung cancer patients at any time point prior to surgery [11]. The majority of the above studies have included both early (stages I/II) and late stage (stages III/IV) NSCLC patients, with the outcome focused on overall survival (OS) or mortality, and patients with different years since smoking cessation were grouped together as ex-smokers. We hypothesized that smoking cessation is associated with improved survival of NSCLC patients, with the strongest association observed in never smokers or long-term ex-smokers. In addition, gender may influence the effect of smoking cessation on lung cancer prognosis. Furthermore, because early stage NSCLC patients have much better survival than late stage patients, we hypothesized that the long-term effects of smoking cessation will be more likely to be observed in early stage patients. We tested these a priori hypotheses in our cohort of early stage NSCLC patients.
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Materials and methods
This study began in 1992 and was approved by the Human Subjects Committee of Massachusetts General Hospital (MGH) and Harvard School of Public Health. Eligible subjects were histologically confirmed and consecutively recruited NSCLC patients at the MGH who were over 18 years old. More than 85% of eligible patients participated in this study, and 96% were Caucasian. Among the 558 incident early stage (stages IA–IIB) NSCLC patients recruited between 1992 and 2002 (accounted for 58% of all stages
Results
The demographic, clinical, treatment, and smoking information on patients by categories of years since smoking cessation are shown in Table 1. No statistically significant differences were found for stage among patients with different years of smoking cessation. Compared with current smokers, long term ex-smokers (e.g. quit ≥18 years) and never smokers were older, had lower frequencies of squamous cell carcinoma and higher frequencies of bronchioloalveolar carcinoma, and lower pack-years of
Discussion
In this cohort of early stage NSCLC patients, subjects who quit smoking seemed to have improved OS or RFS compared to current smokers. The results were consistent in log-rank test and Cox proportional hazard models, before and after adjusting for other covariates, whether smoking cessation time was treated as a categorical variable or as a continuous variable. In addition to classifying ex-smokers by tertiles of time since smoking cessation, we also classified ex-smokers into different groups
Conflict of interest statement
None declared.
Acknowledgments
This study was supported by National Institutes of Health Grants CA 092824, CA074386, CA090578, ES/CA 06409, ES00002, and 5T32CA071345; Flight Attendants Medical Research Institute; American Institute for Cancer Research; and Doris Duke Charitable Foundation. We thank the following staff members of the Lung Cancer Susceptibility Group: Barbara Bean, Jessica Shin, Andrea Shafer, Lucy Ann Principe, Salvatore Mucci, Richard Rivera-Massa, David P. Miller, Thomas Van Geel, Li Su; and the generous
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2016, Clinical ImagingCitation Excerpt :Similar studies reported a survival advantage for former smokers in a different subset of NSCLC patients. Zhou et al. [13] reported a > 30% risk reduction in patients who had quit ≥ 9 years prior to diagnosis in those with early-stage NSCLC compared to current smokers, with Ebbert et al. [14] reporting a significant survival advantage of smoking cessation in females. Smoking cessation has been found to reduce the risk of complications after primary lung cancer resection as well.
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These authors contributed equally to this work.