The association between smoking status and survival in oral cavity squamous cell carcinoma (OSCC) patients remains unclear. Therefore, we evaluated the association between smoking status before treatment and clinical outcome in OSCC patients. We conducted a retrospective cohort study of 222 OSCC patients who were treated at Aichi Cancer Center in Japan. Of these, 82 patients (36.9%) were non-smokers, 65 (29.3%) were light smokers (pack-years smoking (PY) <30), 54 (24.3%) were moderate smokers (30≤PY<60), and 21 (9.5%) were heavy smokers (60≤PY). The survival impact of pre-treatment smoking status was evaluated using multivariate proportional hazard models. Five-year overall survival for non-, light, moderate, and heavy smokers was 72.9% (95% confidence interval CI): (61.4-81.5), 85.5% (74.0-92.2), 59.9% (44.3-72.4) and 69.0% (42.8-85.0). Adjusted hazard ratios (HRs) for moderate and heavy smokers in comparison with light smokers were 2.44 (1.07-5.57, P=0.034) and 2.66 (0.97-7.33, P=0.058) and the dose-response relationship among smokers was statistically significance (P(trend)=0.024). In addition, adjusted HR for non-smokers relative to light smokers was 2.27 (0.84-6.15, P=0.108). We observed a suggestive heterogeneity in the impact of smoking status by treatment method (P for heterogeneity=0.069). Effect of smoking was evident only among the chemoradiotherapy or radiotherapy group. In this study, we found the significant positive dose-response relationship among smokers on clinical outcome in OSCC patients and that non-smokers were worse prognosis than light smokers. In addition, this effect might differ by treatment method.
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