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Comparison of Aspects of Smoking Among Four Histologic Types of Lung Cancer

¹ Harvard School of Public Health, Brigham and Women's Hospital and Harvard Medical School, United States;
² Brigham and Women's Hospital, Harvard Medical School, and Harvard School of Public Health, United States;
³ Washington University School of Medicine, United States

To whom correspondence should be addressed. E-mail: skenfiel{at}hsph.harvard.edu

ABSTRACT
The magnitude of the link between cigarette smoking and lung cancer may vary by histologic type. We used polytomous logistic regression to evaluate whether aspects of smoking have different effects across four histologic types in the Nurses’ Health Study. From 1976 through 2002, we identified 1,062 cases of lung cancer: squamous cell (n=201), small cell (n=236), adenocarcinoma (n=543), and large cell carcinoma (n=82), among 65,560 current or former smokers. Risk reduction after quitting ranged from an 8% reduction (relative risk (RR): 0.92, 95% confidence interval (CI): 0.91, 0.94) to a 17% reduction (RR: 0.83, 95% CI: 0.80, 0.86) per year for adenocarcinoma and small cell carcinoma, respectively, with a 9% reduction observed for large cell carcinoma and an 11% reduction observed for squamous cell carcinoma. The association of age at smoking initiation and former cigarette smoking was similar across types, while the association of smoking duration differed. The risk of adenocarcinoma increased by 6% per year of smoking, compared to 7% for large cell, 10% for squamous cell, and 12% for small cell. The 6% difference between adenocarcinoma and small cell carcinoma is equivalent to a 3.2 to 9.7-fold increase in risk for 20 years of smoking. The effects of the number of cigarettes smoked per day and years since quitting smoking are different across the major types of lung cancer, which are fully appreciated at long durations of smoking and smoking cessation. Smoking prevention and cessation should continue to be the focus of public health efforts to reduce lung cancer incidence and mortality.