Abstract
BACKGROUND: The relative importance of predictive factors for advanced non-small cell lung cancer (NSCLC) patients on epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) treatment remains unclear. MATERIALS AND METHODS: We retrospectively enrolled advanced NSCLC patients with single first-generation EGFR-TKI treatment for ⩾5 years (Y) in Taiwan. Clinical data was collected and compared with those of another cohort with single first-line EGFR-TKI treatment for <5 Y. Plasma cell-free DNA (cfDNA) samples were collected from patient subsets, pre- and post-TKI, in the >5 Y group. RESULTS: Overall, 128 and 278 patients were enrolled in the ⩾5 Y and <5 Y groups, respectively. Significant factors in the multivariate analysis of patients' characteristics including Eastern Cooperative Oncology Group performance status 0-1, postoperative recurrence, without brain metastasis, oligometastasis (each score of 2), female sex, erlotinib use, and without bone metastasis (each score of 1), were incorporated into a risk scoring system. The area under the receiver operating characteristic curve was 0.82 [95% confidence interval (CI): 0.78-0.86]. Of the plasma cfDNA samples from 33 patients in the ⩾5 Y group, only 1 had a T790M in 25 patients without progressive disease. In 27 patients with single agent use for ⩾96 months, 22 (81.5%) received local treatment (surgery or radiotherapy) for the primary lung tumor before and during TKI treatment. CONCLUSION: For NSCLC patients with single first-generation EGFR-TKI use for ⩾5 Y, factors with different relative importance exist and the risk-scoring model is feasible with modest accuracy. The role of local treatment for primary tumors in patients with long-term TKI use requires further investigation.