Clinical significance of age at diagnosis among young non-small cell lung cancer patients under 40 years old: a population-based study

Background: Young non-small cell lung cancer (NSCLC) patients under the age of 40 can further be categorized into different age subgroups. Whether they have homogeneous clinical features and survival outcomes remains unexplored. Methods: Information of 4623 NSCLC patients up to 40 years old from 1988 to 2012 was retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. Clinicopathologic characteristics and survival outcomes were compared between patients diagnosed at 18-30 years old (younger group) and those at 31-40 years old (older group). Results: The proportion of patients in the younger group among all lung cancer patients was stable between 1988 and 2012. However, the proportion of patients in the older group decreased from 1.2% to 0.5%. The younger patients had a higher proportion of adenocarcinoma (P = 0.016), a lower proportion of large cell carcinoma (P = 0.008), a higher proportion of stage I disease (P = 0.002) and a lower proportion of stage III disease (P < 0.001). The younger patients had significantly better lung cancer-specific survival (LCSS) in the whole cohort (P < 0.001) and in the subgroup of patients with stage I (P = 0.038) or stage IV (P < 0.001) disease. Multivariate survival analysis showed that patients under 30 years old was an independent predictor of both better LCSS (P = 0.010) and overall survival (OS) (P = 0.018). Conclusions: Adult NSCLC patients under 30 years old had distinctive clinicopathologic characteristics and survival outcomes compared to patients diagnosed at 31-40 years old.