Abstract: Background and purpose: For patients with advanced lung adenocarcinoma harboring an activating EGFR gene mutation, the current standard of care is EGFR-TKI alone. This study aimed to compare efficacy and safety of gefitinib plus chemotherapy with gefitinib or chemotherapy alone for treating advanced lung adenocarcinoma with an activating EGFR gene mutation. Methods: This study included 61 patients with lung adenocarcinoma harboring an activating EGFR gene mutation (19 exons deletion and exon 21 L858R mutations) whose ECOG performance status was 0 or 1. Patients were randomly divided into 3 groups. Group A (n=20) were given carboplatin/pemetrexed of a 4-week cycle, six cycles at most, plus gefitinib (pemetrexed 500 mg/m², d1; carboplatin AUC 5, d1; gefitinib 250 mg/d, d 5-21), and then received pemetrexed of a 4-week cycle plus gefitinib as maintenance therapy; Group B (n=20) were given carboplatin/pemetrexed of a 4-week cycle, six cycles at most (pemetrexed 500 mg/m2, d1; carboplatin AUC 5, d1), then received pemetrexed as maintenance therapy; Group C (n=21) were given gefitinib (gefitinib 250 mg/d). Patients continued to receive therapy until disease progression or unacceptable toxicity or death. The primary end point was middle PFS and 12 months PFS rate. The secondary end points included objective response rate and adverse events. Results: Groups A and C both lost 1 case during follow-up. Median PFS for patients was 20.1 months (95%CI:18.0-22.2) in group A, 5.5 months (95%CI:3.9- 7.2) in group B, and 9.8 months (95%CI:6.8-12.8) in group C. PFS rates of 12 months for groups A, B and C were 78.9%, 15.0% and 40.0%, respectively. The overall objective response rates for groups A, B and C were 84.2%, 35.0% and 65.0%, respectively. Serious adverse events were reported by 36.8% for group A, 30.0% for group B, and 5.0% for group C. The most common grade 3/4 adverse events were neutropenia (3 cases in group A, 4 cases in group B), fatigue (2 cases in group A, 2 cases in group B) and liver function impairment (2 cases in group A, 1 case in group C). Conclusion: Among patients with EGFR mutant lung adenocarcinoma, combination of chemotherapy with gefitinib as first-line treatment demonstrates an improvement in PFS. Long-term survival results will be further followed up.

Key words: Lung adenocarcinoma, EGFR mutation, Chemotherapy, Gefitinib