Effects of Obesity and Smoking on Survival in Non-Small Cell Lung Cancer

Background: Obesity is an emerging leading cause of morbidity and mortality in the US and the relationship between obesity, tobacco, and survival in NSCLC is unclear. Methods: Data (n = 87,631) were obtained from linkage of the 1996-2007 Florida Cancer Data System to the Agency for Health Care Administration database providing procedure and diagnoses codes. Survival time was calculated from date of diagnosis to date of death. Smoking status was categorized as never, current, and former. Obesity (yes/no) = ICD9 code BMI > 30 kg/m2, cachexia = ICD9 code “wasting syndrome”, & non-obese = non-obese & non cachectic. Cox proportional regression models used to predict survival; demographic, clinical, treatment factors, & comorbidities were included in adjusted models with smoking status and obesity as the main factors. Results: The majority of patients (pts) were either former (49%) or current (40%) smokers, & non-obese (88%). 6.8% of pts were obese & 4.8% of pts were cachectic. There were significant differences between survival curves and median survival (months) for obese vs. non-obese vs. cachectic pts. (20 vs 10 vs. 7.9; P < 0.001). Former and current smokers had shorter median survival than never smokers (10.8 & 9.2 vs. 11.9; P < 0.001). Survival rates (%) at 1-yr (60.1 vs. 45.2 vs. 37.7; P < 0.001), 5-yr (30.3 vs. 15.4 vs. 9.5; P < 0.001), 10-yr (18.1 vs. 7.6 vs. 2.7; P < 0.001) were better for obese vs. non-obese and cachectic pts respectively. Independent predictor of worse survival in the unadjusted model was former (HR 1.08; P < 0.001) and current (HR 1.20; P < 0.001) smokers compared to never. Obese and non-obese pts had better survival vs. cachexia pts. (HR 0.52; P < 0.001 and HR 0.80, p < 0.001 respectively) and obese had better survival than Non-obese pts (HR 0.65, p < 0.001). In the adjusted model, controlling for extensive variables and comorbidities, former (HR 1.11; P < 0.001) and current (HR 1.19; P < 0.001) smokers still had significantly worse survival vs. never smokers. Obese patients still had better survival (HR 0.87; P < 0.001, and HR 0.88, p < 0.001) vs. cachexia patients and non-obese respectively, survival rate was not significantly different compare non-obese with cachexia. Conclusions: Our results show that being a former or current smoker worsens survival while obesity improved survival when compared with cachexia patients or Non-obese.