摘要Background Risk factors that contribute to younger patients with lung cancer are still relatively unknown.The aim of this study was to compare the clinical characteristics,histological types,stages at diagnosis,treatment modalities and survival rates between young and old patients with lung cancer.Methods The study was designed as a retrospective review of all lung cancer patients admitted to the Third Affiliated Hospital of Harbin Medical University from 1998 to 2008.Survival analyses using univariate and multivariate approaches were performed to compare the survival rates between different age groups and to discover potential prognostic factors.Results This research included 3320 patients with primary lung cancer,of whom 626 (18.8％) were 45 years old or younger at the time of diagnosis.The percentage of smokers and the male to female ratios between the young and old patient groups were 51.27％ vs.70.6％ (P ＜0.001) and 1.99 vs.2.13 (P=0.4801),respectively.The young patient group had a higher incidence of adenocarcinoma and fewer surgeries.The 1-year,3-year and 5-year survival rates in the young patient group were generally lower than those of the old patient group,with significant differences (P=0.0232).The clinical stage of the tumor was a prognostic factor for both non-small cell lung cancer patients (P ＜0.0001 ) and small cell lung cancer patients (P=0.0002).Symptoms,diagnostic method,histology,smoking,treatment modality and body mass index were shown to have significant relationships with the survival of lung cancer patients (P ＜0.05).Conclusions Patients with lung cancer who are younger than 45 years old might have a significantly poorer prognosis than that of older patients.Symptoms,diagnosis method,histology,smoking,treatment modality and body mass index can be independent prognostic factors for lung cancer.