Phase I/II Study of Erlotinib to Determine the Optimal Dose in Patients With Non-Small Cell Lung Cancer Harboring Only EGFR Mutations

Abstract

The recommended daily dose of erlotinib was determined for patients with all types of non-small cell lung cancer (NSCLC). We determined the optimal dose (OD) in patients with NSCLC harboring only epidermal growth factor receptor (EGFR) sensitizing mutations. EGFR-tyrosine kinase inhibitor-naïve patients with sensitizing mutations were eligible. Clinical OD was determined in a phase I/II study based on the continual re-assessment method (CRM) of both disease control and dose-limiting toxicity, defined as any toxicity of grade 2 (G2) or higher within 8 weeks. We also determined the pharmacologic OD via a pharmacokinetic (PK) study. Thirty-eight patients were enrolled. Clinical OD was 25 mg/day by the CRM. Median progression-free survival (mPFS) was 9.3 months. In receiver operating characteristic (ROC) analysis of mPFS, the trough concentration ( $C_{min}^{\text{ss}}$ ) was ≥ 0.30 μg/mL. The area under the curve (AUC) and $C_{min}^{\text{ss}}$ were predicted via population PK (PopPK) or a bootstrap of 100 iterations (PopPK₁₀₀ ). TOX20 was defined as < 20% duration of any toxicity ≥ G2 during the PFS period. In ROC analysis of mPFS and TOX20 in the PopPK₁₀₀ study, $C_{min}^{\text{ss}}$ was ≥ 0.17 and < 0.32 μg/mL, respectively. In ROC analysis of mPFS and TOX20 in the PopPK₁₀₀ study, $C_{min}^{\text{ss}}$ was ≥ 0.15 and < 0.31 μg/mL, AUC was ≥ 14.4 and < 14.5 μg/mL•hour, and the dosage was ≥ 58.4 and < 58.8 mg/day, respectively. Clinical and pharmacologic ODs were 25 by CRM and 50-60 mg/day by PK, respectively. The proposed starting OD is 50-60 mg/day, with personalized adjustment of 0.15-0.31 μg/mL based on $C_{min}^{\text{ss}}$ as determined by PopPK monitoring.