Tumor Volume Decrease at 8 Weeks Is Associated with Longer Survival in EGFR-Mutant Advanced Non-Small-Cell Lung Cancer Patients Treated with EGFR TKI

Background: The study investigated whether tumor volume changes at 8 weeks of therapy is associated with outcomes in advanced non-small-cell lung cancer (NSCLC) patients harboring sensitizing epidermal growth factor receptor (EGFR) mutations treated with EGFR tyrosine kinase inhibitors (TKIs). Methods: In 56 advanced NSCLC patients with sensitizing EGFR mutations treated with first-line erlotinib or gefitinib, tumor volumes of dominant lung lesions were measured on baseline and follow-up computed tomography, and were analyzed for association with survival. Results: Among 56 eligible patients, the median tumor volume was 17.8cm(3) (range, 1.3-172.7cm(3)) on the baseline scans. Forty-nine patients had follow-up computed tomography at approximately 8 weeks; the median tumor volume at 8 weeks was 7.1cm(3) (range, 0.4-62.3cm(3)), with the median proportional volume change of -59% (range, -90% to +91%) from baseline. The proportional volume change at 8 weeks was associated with survival (p = 0.02). Using the cutoff value of 38% volume decrease (75th percentile) at 8 weeks, patients with volume decrease more than 38% (n = 37) had a median overall survival of 43.5 months compared with 16.3 months among those with volume decrease of 38% or less (n = 12; p = 0.01). The median progression-free survival for patients with more than 38% volume decrease was 12.6 months, compared with 5.5 months for those with 38% or lesser volume decrease (p = 0.2). Conclusion: The proportional volume change at 8 weeks is associated with overall survival in EGFR-mutant advanced NSCLC patients treated with first-line EGFR-TKIs. The observation of the study, if confirmed in larger study cohorts, indicates that tumor volume analysis at 8 weeks may provide an early marker for survival, and contribute to therapeutic decision making by identifying patients who may benefit from additional anticancer therapy after 8 weeks of EGFR-TKI therapy.