Factors associated with overall survival in a population-based cohort of non- squamous NSCLC patients from northern New Zealand: A comparative analysis by EGFR mutation status.

Background: Previous studies have reported inconsistent results regarding the effect of epidermal growth factor receptor (EGFR) mutations on overall survival in patients with non-squamous non-small-cell lung cancer (NSCLC). This study assesses the effect of EGFR mutation on overall survival, and how the effects of other survival predictors differ by EGFR mutation status.

Methods: The study used a population- based cohort of 1534 non-squamous NSCLC patients diagnosed in northern New Zealand between 1st February 2010 and 31st July 2017. Cox regression survival analyses were used to explore the associations between clinicopathological factors and overall survival by EGFR mutation status. The factors included were age at diagnosis, sex, ethnicity, smoking status, performance status, metastasis status and tumour site.

Results: In this cohort, 20% had anEGFR mutation. The median overall survival times were 0.8 years and 2.79 years in EGFR-mutation-negative and -positive groups, respectively (p < 0.0001). Metastasis at diagnosis showed large effects on overall survival in both EGFR-mutation- negative (hazard ratio (HR) = 3.6) and mutation-positive (HR = 3.3) groups. In subgroup analyses by mutation status and metastasis, females had lower survival only if they were mutation-positive; Māori had lower survival (than European New Zealanders) only if the disease was metastatic, and tumour site had significant effects only in patients without metastasis. Age, performance status and smoking status showed consistent effects in all subgroups.

Conclusion: EGFR mutation status and metastasis are the main predictors for overall survival in non-squamous NSCLC patients. The effects of sex, ethnicity and tumour site vary depending on EGFR mutation and metastasis status.