Factors associated with the prognosis and long-term survival of patients with metastatic lung adenocarcinoma: a retrospective analysis

Background: Outcome of patients with advanced non-small cell lung cancer (NSCLC) treated with platinum-based doublet chemotherapy is usually poor, with overall survival ranges from 8-13 months. However, the overall survival is improved to 21-28 months in the era of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). This study aimed to explore the prognostic factors to predict long-term survival in the era of EGFR TKI. Methods: A total 1,030 patients were studied who had been diagnosed with metastatic adenocarcinoma of lung from January 2005 to December 2009 at Linkou Chang Gung Memorial Hospital. Long-term survivors (LTS) were defined as patients who survived five years or more after the initial diagnosis of stage IV disease. Data on patient age, gender, smoking status, performance status at diagnosis, TNM stage, metastatic pattern, number of metastases, and organs with tumor involvement, EGFR gene mutation status, types of treatment received, EGFR TKI treatment and longest EGFR TKI duration were retrospectively obtained from medical charts. We calculated the odds ratio (OR) of long-term survival from collected clinical parameters to predict long-term survival. Results: In this large retrospective study, we reported a five-year survival of 5.0% among patients with metastatic adenocarcinoma of lung. A total 52 LTS and 978 non-LTS were identified. Patients had more contralateral or pleural/pericardial metastases in the LTS group than in the non-LTS group (51.9% vs. 19.0%, P<0.001), while less extrathoracic spread than in the non-LTS group (42.3% vs. 79.6%, P<0.001). The mutation of the EGFR gene was more frequent in the LTS group than in the non-LTS group (19.2% vs. 7.1%, P=0.006). Conclusions: In conclusion, our results suggest that an age younger than 60 years, absence of extrathoracic spread and EGFR TKI treatment duration of more than one year play an important role in the long-term for survivors who survive for more than 5 years.