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

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 ( [Formula: see text]) was ≥ 0.30 μg/mL. The area under the curve (AUC) and [Formula: see text] were predicted via population PK (PopPK) or a bootstrap of 100 iterations (PopPK(100)). TOX20 was defined as < 20% duration of any toxicity ≥ G2 during the PFS period. In ROC analysis of mPFS and TOX20 in the PopPK(100) study, [Formula: see text] was ≥ 0.17 and < 0.32 μg/mL, respectively. In ROC analysis of mPFS and TOX20 in the PopPK(100) study, [Formula: see text] 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 [Formula: see text] as determined by PopPK monitoring.