Impact of number versus location of metastases on survival in stage IV M1b non-small cell lung cancer

To assess the impact of location versus number of extra-pulmonary metastatic sites (EPMS) on survival in stage IV non-small cell lung cancer (NSCLC). Retrospective analysis was conducted on patients diagnosed during 1999-2013 with stage IV, M1b (AJCC 7th edition) NSCLC using the large, institutional Glans-Look Database, which contains patient demographic, clinical, pathological, treatment, and outcome information. We assessed the impact of location and number of EPMS and identified correlates of overall survival using the Kaplan-Meier method and Cox regression. We identified a total of 2065 NSCLC patients with EPMS. Median age was 67 (IQR 58-75) years, 52% were men, and 78% were current or former smokers. 60% had one EPMS, and 40% had two or more EPMS. Among those with only one EPMS, most frequent organ involvement included bone (40%), brain (32%), and liver (13%). Median overall survival (mOS) was worst in those with liver metastasis and best in those with adrenal metastasis (2.0 vs. 5.2 months, p = 0.015). However, outcomes based on site of organ involvement were not significantly different in multivariable analysis. Compared to patients with one EPMS, individuals with two or more EPMS experienced worse outcomes (mOS 2.9 vs. 3.9 months, p < 0.001), and were associated with worse prognosis in Cox regression analysis (HR 1.5, 95% CI 1.3-1.7, p < 0.001). Number rather than location of EPMS is a prognostic factor in patients with stage IV M1b NSCLC. This information is relevant for accurate prognostication, stratification of participants in future clinical trials, and timely and appropriate advanced care planning.