Clinical Impact of Post-Progression Survival on Overall Survival in Elderly Patients with Non-Small-Cell Lung Cancer Harboring Sensitive EGFR Mutations Treated with First-Line EGFR Tyrosine Kinase Inhibitors

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Background/Aims: More than 50% of patients with lung cancer are aged > 65 years, and non-small-cell lung cancer (NSCLC) accounts for 85% of all cases of lung cancer among both elderly and adult patients. Subsequent therapies confound the capability to discern the effect of first-line chemotherapy on overall survival (OS). Therefore, using individual-level data, our study aimed to determine the relationships of progression-free survival (PFS) and post-progression survival (PPS) with OS after first-line epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) treatment in elderly patients with NSCLC harboring sensitive EGFR mutations. Methods: Between April 2008 and December 2015, we analyzed 68 elderly patients with NSCLC harboring sensitive EGFR mutations and treated with first-line EGFR-TKI. The relationships of PFS and PPS with OS were analyzed at an individual level. Results: Linear regression analysis showed that PPS was more closely associated with OS (R² = 0.54) than PFS was (R² = 0.48). Best response at first-line treatment, performance status at the end of first-line treatment, and administration of EGFR-TKI rechallenge were significantly correlated with PPS. Conclusions: PPS has a stronger impact on OS than PFS does in elderly patients with NSCLC harboring sensitive EGFR mutations and treated with first-line EGFR-TKI. These results indicate that OS in this patient population may be influenced by treatments subsequent to first-line chemotherapy; however, this remains to be verified in prospective studies.