Background: Lung cancer and chronic obstructive pulmonary disease (COPD) are leading causes of morbidity and mortality in the United States. Cigarette smoking is associated with both lung cancer and COPD, but whether COPD independently predicts lung cancer risk is debated. To examine this question in a large, prospective study, we constructed risk models using data from the observational study arm of the Women's Health Initiative.

Methods: Initial analyses included 89,384 women (n = 1,479 lung cancers) with complete baseline information on cigarette smoking and COPD status. We created a second, time-varying model to account for incident smoking that occurred during the eight year follow up period, in addition to the number of pack years reported at baseline. Estimates from Cox proportional hazard models were used to assess the association between COPD and lung cancer. The baseline hazard was stratified by age at study entry in all models. COPD status was self-reported, and diagnoses within one year of lung cancer diagnoses were not included. Reported lung cancers were adjudicated via medical record.

Results: There was an interaction between number of pack years (continuous) of smoking at baseline and COPD status (p<0.001). Never smokers with COPD were 2.7 times more likely to develop lung cancer compared to never smokers without COPD, after adjusting for race, education, income and body mass index (HR = 2.70, 95% CI: 2.12, 3.45). Similar risk of lung cancer associated with COPD was seen among smokers with 20 pack years of smoking (HR = 2.37, 95% CI: 1.96, 2.87) and at 40 pack years of smoking (HR = 2.08, 95% CI: 1.77, 2.45) after adjustment. From the time-varying models, women with COPD had approximately 2 times the risk of developing lung cancer compared to those who did not, after adjusting for smoking, race, education, income and body mass index (HR = 1.90, 95% CI: 1.54, 2.34). COPD was associated with all subtypes of lung cancer after adjustment for smoking, with hazard ratios ranging from 1.59-2.15 for different histological subtypes of non-small cell lung cancers. Smokers with COPD were 4.6 times more likely to develop small cell lung cancers compared to those without COPD (HR = 4.68, 95% CI: 2.67, 8.20).

Conclusion: These data suggest that COPD is an independent risk factor for the development of lung cancer, and should be considered when constructing risk models.

Citation Format: Michele L. Cote, Amy Lehman, Rowen Chlebowski, Brittany Haynes, Gloria Ho, Manali Patel, Lori Sakoda, Michael Simon, Heather Wakelee, Ann Schwartz. COPD and risk of lung cancer in post-menopausal women: findings from the Women's Health Initiative. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 835. doi:10.1158/1538-7445.AM2015-835