Definitive radiotherapy for stage I nonsmall cell lung cancer: a population-based study of survival.

BACKGROUND: The current study characterizes the overall survival (OS) and cause-specific survival (CSS) of patients with stage I nonsmall cell lung cancer (NSCLC) who were treated with radiotherapy alone, and analyzes the variables potentially affecting survival outcomes.
METHODS: A total of 8524 patients with stage I NSCLC (according to the sixth edition of the American Joint Committee on Cancer staging manual) who were diagnosed between 1988 and 2008 were retrospectively analyzed using the population-based Surveillance, Epidemiology, and End Results database. Cox regression analysis was used to calculate hazard ratios (HR) from multivariate analyses.
RESULTS: The 1-year, 2-year, and 5-year OS rates were 62%, 37%, and 11%, respectively; the corresponding lung cancer CSS survival rates were 68%, 45%, and 20%, respectively. Approximately 77% of deaths were from lung cancer (5292 of 6891 total deaths). Cardiac (n = 477 deaths) and pulmonary (other than lung cancer deaths; n = 475 deaths) deaths accounted for 14% of deaths. From Cox proportional hazards analyses, male sex (HR, 1.2) and squamous cell carcinoma histology (HR, > 1.1) were found to be significantly (P < .0001) adverse prognostic factors for both OS and lung cancer CSS. A more recent calendar year of diagnosis was associated with significantly (P < .0001) improved OS (HR, 0.84 per decade) and lung cancer CSS. This trend was also significant (P < 0.0001) when restricting analyses to those patients with tumors measuring ≤ 5 cm (n = 5402 patients). T1 classification (vs T2 or T unknown) and smaller tumor size were found to be significantly (P < .0001) favorable factors.
CONCLUSIONS: From a population-based registry analysis of patients with stage I NSCLC, significant (albeit modest) improvements in survival in more recent years were appreciated, which likely reflect technologic advances in the diagnosis of, staging of, and radiotherapy for NSCLC.