Tumor Growth Rate After Nadir Is Associated With Survival in Patients With <i>EGFR</i>-Mutant Non-Small-Cell Lung Cancer Treated With Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor.

Abstract

To investigate the association between tumor volume growth rate after the nadir and survival in patients with <i>EGFR</i>-mutant advanced non-small-cell lung cancer (NSCLC) treated with erlotinib. Seventy-one patients with <i>EGFR</i>-mutant advanced NSCLC treated with erlotinib were studied for computed tomography tumor volume kinetics during therapy. The tumor growth rate after nadir was obtained using a previously published analytic module for longitudinal volume tracking to study its relationship with overall survival (OS). The median tumor volume for the cohort was 19,842 mm³ at baseline and 4,083 mm³ at nadir. The median time to nadir was 6.2 months. The tumor growth rate after nadir for log_eV (the natural logarithm of tumor volume measured in mm³) was 0.11/mo on average for the cohort (SE: 0.014), which was very similar to the previously validated reference value of 0.12/mo to define slow and fast tumor growth. The OS of 48 patients with slow tumor growth (≤ 0.12/mo) was significantly longer compared with 23 patients with fast tumor growth (> 0.12/mo; median OS: 37.8 <i>v</i> 25.0 months; <i>P</i> = .0012). In Cox models, tumor growth rate was also associated with survival (regression coefficient: 3.9903; <i>P</i> = .0024; faster rate leads to increased hazards), after adjusting for time to nadir (regression coefficient: -0.0863; <i>P</i> = .0008; longer time to nadir leads to decreased hazards) and smoking history. In patients with <i>EGFR</i>-mutant advanced NSCLC treated with erlotinib, slower tumor growth rates after nadir were associated with longer OS, providing a rationale for using tumor growth rates to guide precision therapy for lung cancer.