Smoking at diagnosis is an independent prognostic factor for cancer-specific survival in head and neck cancer: findings from a large, population-based study.

BACKGROUND Some studies suggest smoking may result in poorer clinical outcomes in head and neck cancer, but the evidence is heterogeneous and some of it is poor quality. In a large, population-based, study we investigated: (i) whether smoking at diagnosis is an independent prognostic factor for cancer-specific survival in head and neck cancer; and (ii) whether the association varies by site and treatment. METHODS Head and neck cancers (ICD10 C01-C14, and C30-32) diagnosed from 1994 to 2009 were abstracted from the National Cancer Registry Ireland, and classified by smoking status at diagnosis. Follow-up was for 5 years or until December 31, 2010. Multivariate Cox proportional hazards models were used to compare cancer-specific death rates in current, ex-, and never smokers. Subgroup analyses by site and treatment were conducted. RESULTS In total, 5,652 head and neck cancers were included. At diagnosis, 24% were never smokers, 20% ex-smokers, and 56% current smokers. Compared with never smokers, current smokers had a significantly raised death rate from cancer [multivariate HR, 1.36; 95% confidence interval (CI), 1.21-1.53]. The association was similar after restriction to squamous cell tumors. A significantly increased cancer-related death rate was seen for current smokers with oral cavity, pharyngeal, and laryngeal cancers. The association was stronger in surgically treated patients [HR, 1.49; 95% CI, 1.25-1.79; P(interaction) = 0.01]. Neither radiotherapy nor chemotherapy modified the effect of smoking. CONCLUSIONS Patients with head and neck cancer who smoke at diagnosis have a significantly increased cancer death rate. IMPACT Greater efforts are needed to encourage and support smoking cessation in those at risk of, and diagnosed with, head and neck cancer.