Definitive Radiation for Stage I Non-small Cell Lung Cancer: A Population-based Study of Survival

Abstract

Michael T. Milano, MD PhD, Hong Zhang, PhD MD, Kenneth Y. Usuki, Deepinder P. Singh, MD, Yuhchyau Chen, PhD MD Department of Radiation Oncology, University of Rochester Medical Center, Rochester, NY 14642 Abstract * Purpose: To characterize overall survival (OS) and cause-specific survival (CSS) of patients with Stage I non-small cell lung cancer (NSCLC) treated with radiation alone, and analyzes potential prognostic variables. * Methods and Materials: A total of 8,524 Stage I NSCLC (6th edition of AJCC) patients, diagnosed from 1988-2008, were retrospectively analyzed using the population-based Surveillance, Epidemiology, and End Results database. Patients were grouped into four eras: 1988-1995, 1996-2000, 2001-2004 and 2005-2008. Cox regression was used to calculate hazard ratios (HR) from multivariate analyses. * Results: The median age at the time of NSCLC diagnosis was 74 years. While age at diagnosis significantly increased with more recent calendar year of NSCLC diagnosis, this change was modest. Other significant changes observed with more recent year of diagnosis include relatively more females (38% prior to 1996, and 48% from 1996-2008, p 1.1) were significantly (p<0.0001) adverse prognostic factors for both OS and lung cancer CSS. A more recent calendar year of diagnosis was associated with significantly (p<0.0001) improved OS and lung cancer CSS (HR 0.84 and 0.82 per decade respectively). This trend was also significant (p<0.0001) when restricting analyses to those patients with tumor size ≤5 cm (n=5,402 patients, representing Stage I NSCLC in the AJCC 7th edition). T1 stage (versus T2 or T unknown) and smaller tumor size were also significantly (p<0.0001) favorable factors. * Conclusions: From a hypothesis generating, retrospective, population-based registry analysis of patients Stage I NSCLC, more recent calendar year of diagnosis, female gender, non-squamous cell carcinoma histology, earlier T stage, and smaller size were associated with more favorable OS and lung cancer CSS outcomes. Improvements in survival in more recent years, even when correcting for other prognostic factors in Cox regression analyses, likely reflects technologic improvements in lung cancer diagnosis, staging and radiotherapy delivery.