Survival outcome of non-small cell lung cancer patients: Comparing results between the database of the Comprehensive Cancer Center Zürich and the Epidemiological Cancer Registry Zurich and Zug

Background: Cancer cases among the population of the canton Zurich, are registered in the Cancer Registry of the cantons of Zurich and Zug (KKR). The Thoracic Oncology Center, founded in 2011 is one of 17 multidisciplinary centers within the Comprehensive Cancer Center Zurich (CCCZ).

Methods: The aim of the current study is to quantify the mortality risk of patients with NSCLC and identify differences on survival and other factors between patients receiving their primary treatment at the CCCZ and those treated elsewhere and registered by KKR. The differential effect between CCCZ and KKR cohorts on survival: overall, by stage, sex and age, is explored. Stratified log-rank and Wilcoxon tests, Cox models and restricted mean survival times (RMST) are estimated. Propensity score matching (PSM) is also used to adjust for confounding factors.

Results: Analysis included 848 NSCLC cases from the CCCZ and 1759 from the KKR, diagnosed between January 2011 and December 2015. At a median follow-up of 57 months, overall survival (OS) was significantly superior for patients treated at the CCCZ compared to KKR [Median OS: 36.0 months (95%CI: 31.0-45.0) and 12.0 months (95%CI: 11.0-13.0), respectively, stratified log-rank p < 0.001; adjusted HR = 1.31, (95% CI: 1.18-1.46), difference in RMST up to 72 months: 13.8 months (95%CI: 11.5-16.2), p < 0.001]. The effect of cohort was significant for stages III and IV (overall and also by sex and age). After PSM OS remained significantly superior for patients treated at the CCCZ compared to KKR.

Conclusions: The survival probability for patients in the CCCZ cohort was superior to that of patients in the canton Zürich treated outside the center. This analysis provides further evidence of the importance of the volume of experience and the availability of a multidisciplinary organization and research environment, as delivered by a comprehensive cancer center, on the outcome of patients with NSCLC.