Impact of Smoking on Cancer Stage at Diagnosis

Abstract

Background: Studies evaluating the relationship between smoking and cancer spread are limited. Methods: We studied the relationship between cancer stage at diagnosis (local, regional, or metastatic) and smoking history (current, previous, or nonsmoker). For lung cancer, patterns of spread were also studied. Results: In a tumor registry for eastern North Dakota, northwestern Minnesota, and northern South Dakota, 11,716 cases were identified from 1986 to 2001. Current smokers (relative risk [RR], 2.11; 95% confidence interval, 1.93 to 2.32; P < .001) and previous smokers (RR, 1.56; 95% confidence interval, 1.42 to 1.72; P < .001) had an increased risk of metastatic disease at diagnosis. Current smokers (RR, 1.39; 95% confidence interval, 1.29 to 1.51; P < .001), but not previous smokers, also had an increased risk of regional disease. An increase in metastatic disease was most evident for prostate cancer (RR, 1.53; P = .003). An increase in regional disease was most evident for head and neck (RR, 3.53; P < .001), prostate (RR, 1.83; P = .030), and breast cancer (RR, 1.22; P = .005). Compared with previous smokers, current smokers with metastatic lung cancer were more likely to have involvement of the brain (33.6% v 23.0%; P = .004), bone marrow, adrenal gland, and pericardium (24.7% v 15.9%; P = .004). Conclusion: Previous or current smoking is a risk factor for increased cancer stage in a wide range of malignancies. Further study is required to determine whether this association is causal.