Abstract
BACKGROUND: We aimed to examine whether patients with de novo and relapsed/progressed stage IIIB-IV non-small cell lung cancer (NSCLC) without epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) mutations have different prognoses. METHODS: This retrospective study analyzed the Health Insurance Review and Assessment claims data in South Korea from 2013 to 2020. Patients with stage IIIB-IV NSCLC without EGFR or ALK mutations who received first-line palliative therapy between 2015 and 2019 were identified. Overall survival (OS), time to first subsequent therapy (TFST), and time to second subsequent therapy (TSST) were estimated using the Kaplan-Meier method. Multivariate Cox regression analysis was used to reveal the impact of de novo versus relapsed/progressed disease on OS. Treatment patterns, including treatment sequence, top five most frequent regimens, and time to treatment discontinuation, were described in both groups. RESULTS: Of 14,505 patients, 12,811 (88.3%) were de novo, and 1,694 (11.7%) were relapsed/progressed. The median OS in the de novo group was 11.0 versus 11.5 months in the relapsed/progressed group (P = 0.002). The ongoing treatment probability was higher in relapsed/progressed patients than in de novo patients from 6.4 months since the initiation of first-line treatment (P < 0.001). Median TSST was shorter in the de novo group than in the relapsed/progressed group (9.5 vs. 9.9 months, P < 0.001). In multivariate analysis, de novo disease was associated with shorter OS (hazard ratio 1.07; 95% confidence interval 1.01-1.14). The overall treatment patterns for de novo and relapsed/progressed patients were similar. CONCLUSIONS: De novo patients had poorer OS and TSST after the initiation of palliative therapy than relapsed/progressed patients. These findings suggest that the stage of the disease at the time of initial diagnosis should be considered in observational studies and clinical trials as a prognostic factor.